diff --git a/src/org/ntlab/traceDebugger/DebuggingController.java b/src/org/ntlab/traceDebugger/DebuggingController.java
index 755d204..0d7790b 100644
--- a/src/org/ntlab/traceDebugger/DebuggingController.java
+++ b/src/org/ntlab/traceDebugger/DebuggingController.java
@@ -285,7 +285,7 @@
 		refresh(null, debuggingTp, false);
 		return true;
 	}
-	
+
 	public boolean stepOverAction() {
 		if (!isRunning) return false;
 		if (debuggingTp == null) return false;
@@ -298,28 +298,13 @@
 		int currentLineNo = debuggingTp.getStatement().getLineNo();
 		boolean isReturned = false;
 
-		// �X�e�b�v�I�[�o�[��p���ē��B�_�����‚��Ă���
-		TracePoint startTp = debuggingTp.duplicate();
 		while (!(isReturned = !(debuggingTp.stepOver()))) {
 			if (currentLineNo != debuggingTp.getStatement().getLineNo()) break;
 			previousTp = debuggingTp.duplicate();
 		}
-		TracePoint goalTp = debuggingTp.duplicate();
-		if (!isReturned) {
-			// �X�e�b�v�t����p���č��x�͌Ăяo����ɂ�����Ȃ���\�ߌ��‚��Ă��������B�_�܂Ői�܂��� (�ϐ������X�V�̂��ߓr���̃A�b�v�f�[�g��S�ďE��)
-			debuggingTp = startTp;
-			do {
-				Statement statement = debuggingTp.getStatement();
-				if (statement.equals(goalTp.getStatement())) break;
-				if (statement instanceof FieldUpdate || statement instanceof ArrayUpdate) {
-					Variables.getInstance().addDifferentialUpdatePoint(debuggingTp);
-				}
-			} while (debuggingTp.stepFull());			
-		} else {
-			debuggingTp = goalTp;
+		if (isReturned) {
 			while (!debuggingTp.stepOver()); // �Ăяo�����ł̎��̃X�e�[�g�����g�܂Ői�߂�
 		}
-
 		if (debugExecutionIsTerminated(debuggingTp)) return false;
 		refresh(previousTp, debuggingTp, isReturned, true);
 		return true;
@@ -345,7 +330,7 @@
 		refresh(previousTp, debuggingTp, true);
 		return true;
 	}
-	
+
 	public boolean stepNextAction() {
 		if (!isRunning) return false;
 		if (debuggingTp == null) return false;
@@ -355,27 +340,13 @@
 		}
 		TracePoint previousTp = debuggingTp;
 		debuggingTp = debuggingTp.duplicate();
-		TracePoint startTp = debuggingTp.duplicate();
 		boolean isReturned = !(debuggingTp.stepNext());
-		TracePoint goalTp = debuggingTp.duplicate();
-		if (!isReturned) {
-			// �X�e�b�v�t����p���č��x�͌Ăяo����ɂ�����Ȃ���\�ߌ��‚��Ă��������B�_�܂Ői�܂��� (�ϐ������X�V�̂��ߓr���̃A�b�v�f�[�g��S�ďE��)
-			debuggingTp = startTp;
-			do {
-				Statement statement = debuggingTp.getStatement();
-				if (statement.equals(goalTp.getStatement())) break;
-				if (statement instanceof FieldUpdate || statement instanceof ArrayUpdate) {
-					Variables.getInstance().addDifferentialUpdatePoint(debuggingTp);
-				}
-			} while (debuggingTp.stepFull());			
-		} else {
-			debuggingTp = startTp;
+		if (isReturned) {
 			while (!debuggingTp.stepOver()); // �Ăяo�����ł̎��̃X�e�[�g�����g�܂Ői�߂�
 		}
-
 		if (debugExecutionIsTerminated(debuggingTp)) return false;
 		refresh(previousTp, debuggingTp, isReturned, true);
-		return true;	
+		return true;
 	}
 	
 	public boolean resumeAction() {
diff --git a/src/org/ntlab/traceDebugger/Variables.java b/src/org/ntlab/traceDebugger/Variables.java
index b0e5bbb..b22e95d 100644
--- a/src/org/ntlab/traceDebugger/Variables.java
+++ b/src/org/ntlab/traceDebugger/Variables.java
@@ -1,8 +1,6 @@
 package org.ntlab.traceDebugger;
 
 import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -20,12 +18,12 @@
 import org.ntlab.traceAnalysisPlatform.tracer.trace.Statement;
 import org.ntlab.traceAnalysisPlatform.tracer.trace.TracePoint;
 import org.ntlab.traceDebugger.Variable.VariableType;
+import org.ntlab.traceDebugger.analyzerProvider.VariableUpdatePointFinder;
 
 public class Variables {
 	private static final Variables theInstance = new Variables();
 	private List<Variable> roots = new ArrayList<>();
 	private List<MyTreeNode> rootTreeNodes = new ArrayList<>();
-	private Map<String, List<TracePoint>> containerIdToDifferentialUpdateTracePoints = new HashMap<>(); // �ϐ������X�V�ӏ����L��
 	public static final String VARIABLE_TYPE_KEY = "variableType";
 	
 	public static Variables getInstance() {
@@ -134,25 +132,6 @@
 			addAdditionalAttributes(child, idSet, additionalAttributes);
 		}
 	}
-
-	public void addDifferentialUpdatePoint(TracePoint tp) {
-		Statement statement = tp.getStatement();
-		String containerId = null;
-		if (statement instanceof FieldUpdate) {
-			FieldUpdate fu = (FieldUpdate)statement;
-			containerId = fu.getContainerObjId();
-		} else if (statement instanceof ArrayUpdate) {
-			ArrayUpdate au = (ArrayUpdate)statement;
-			containerId = au.getArrayObjectId();
-		}
-		if (containerId == null) return;
-		List<TracePoint> tracePoints = containerIdToDifferentialUpdateTracePoints.get(containerId);
-		if (tracePoints == null) {
-			tracePoints = new ArrayList<TracePoint>();
-			containerIdToDifferentialUpdateTracePoints.put(containerId, tracePoints);
-		}
-		tracePoints.add(tp.duplicate());
-	}
 		
 	public void updateForDifferential(TracePoint from, TracePoint to, boolean isReturned) {
 		updateForDifferential(to);
@@ -162,37 +141,36 @@
 	
 	private void updateForDifferential(TracePoint before) {
 		for (Variable variable : roots) {
-			updateForDifferential(variable, new HashSet<String>(), before);
+			updateForDifferental(variable, before);
 		}
-		containerIdToDifferentialUpdateTracePoints.clear();
 	}
-
-	private void updateForDifferential(Variable variable, Set<String> hasCheckedObjectIdSet, TracePoint before) {
+	
+	private void updateForDifferental(Variable variable, TracePoint before) {
 		variable.setBeforeTracePoint(before);
-		Set<String> containerIdList = containerIdToDifferentialUpdateTracePoints.keySet();
-		String containerId = variable.getContainerId();
-		if (containerIdList.contains(containerId)) {
-			for (TracePoint tp : containerIdToDifferentialUpdateTracePoints.get(containerId)) {
-				Statement statement = tp.getStatement();
+		String objectId = variable.getContainerId();
+		String variableName = variable.getFullyQualifiedVariableName();
+		if (variableName.contains("[")) {
+			// note: �z��̏ꍇ�̓C���f�b�N�X�݂̂����o��
+			String arrayIndexName = variable.getVariableName();
+			variableName = arrayIndexName.substring(arrayIndexName.indexOf("[") + 1, arrayIndexName.lastIndexOf("]"));
+		}
+		
+		TracePoint lastUpdatePoint = variable.getLastUpdatePoint();
+		TracePoint updateTracePoint = VariableUpdatePointFinder.getInstance().getPoint(objectId, variableName, before);
+		if (updateTracePoint != null) {
+			Statement statement = updateTracePoint.getStatement();
+			if (lastUpdatePoint == null || !(statement.equals(lastUpdatePoint.getStatement()))) {
 				if (statement instanceof FieldUpdate) {
 					FieldUpdate fu = (FieldUpdate)statement;
-					if (variable.getFullyQualifiedVariableName().equals(fu.getFieldName())) {
-						updateForDifferentialField(variable, fu.getValueClassName(), fu.getValueObjId(), tp);						
-					}
+					updateForDifferentialField(variable, fu.getValueClassName(), fu.getValueObjId(), updateTracePoint);
 				} else if (statement instanceof ArrayUpdate) {
 					ArrayUpdate au = (ArrayUpdate)statement;
-					String fullyQualifiedVariableName = variable.getFullyQualifiedVariableName();
-					if (fullyQualifiedVariableName.contains("[" + au.getIndex() + "]")) {
-						updateForDifferentialField(variable, au.getValueClassName(), au.getValueObjectId(), tp);
-					}
+					updateForDifferentialField(variable, au.getValueClassName(), au.getValueObjectId(), updateTracePoint);
 				}
 			}
 		}
-		HashSet<String> hasCheckedObjectIdSetOnNext = new HashSet<>(hasCheckedObjectIdSet);
-		hasCheckedObjectIdSetOnNext.add(variable.getContainerId());
 		for (Variable child : variable.getChildren()) {
-			if (hasCheckedObjectIdSetOnNext.contains(child.getContainerId())) continue;
-			updateForDifferential(child, hasCheckedObjectIdSetOnNext, before);
+			updateForDifferental(child, before);
 		}
 	}
 	
@@ -358,7 +336,6 @@
 	public void resetData() {
 		roots.clear();
 		rootTreeNodes.clear();
-		containerIdToDifferentialUpdateTracePoints.clear();
 	}
 	
 	private void resetSpecialValues() {