diff --git a/src/org/ntlab/traceDebugger/analyzerProvider/DeltaExtractionAnalyzer.java b/src/org/ntlab/traceDebugger/analyzerProvider/DeltaExtractionAnalyzer.java
index 1be49c6..c60ee1e 100644
--- a/src/org/ntlab/traceDebugger/analyzerProvider/DeltaExtractionAnalyzer.java
+++ b/src/org/ntlab/traceDebugger/analyzerProvider/DeltaExtractionAnalyzer.java
@@ -46,13 +46,17 @@
 		String dstClassName = variable.getValueClassName();
 		TracePoint before = variable.getBeforeTracePoint();
 		before = before.duplicate();
-		before.stepNext();
 		Reference reference = new Reference(srcId, dstId, srcClassName, dstClassName);
-		reference.setCollection(srcClassName.startsWith("java.util.")); // true�ɂ���ƃR���N�V�����ȊO���o�ł��Ȃ��Ȃ�
+		DeltaRelatedAliasCollector aliasCollector = new DeltaRelatedAliasCollector(srcId, dstId);
+		if (before.getStatement() instanceof FieldUpdate) {
+			extractedStructure = deltaExtractor.extract(before.duplicate(), aliasCollector);
+		} else {
+			before.stepNext();
+			reference.setCollection(srcClassName.startsWith("java.util.")); // true�ɂ���ƃR���N�V�����ȊO���o�ł��Ȃ��Ȃ�	
+			extractedStructure = deltaExtractor.extract(reference, before.duplicate(), aliasCollector);
+		}
 		
 		// �f���^���o
-		DeltaRelatedAliasCollector aliasCollector = new DeltaRelatedAliasCollector(srcId, dstId);
-		extractedStructure = deltaExtractor.extract(reference, before.duplicate(), aliasCollector);
 		MethodExecution creationCallTree = extractedStructure.getCreationCallTree();
 		MethodExecution coordinator = extractedStructure.getCoordinator();
 		TracePoint bottomPoint = findTracePoint(reference, creationCallTree, before.getStatement().getTimeStamp());
diff --git a/src/org/ntlab/traceDebugger/analyzerProvider/DeltaExtractorJSON.java b/src/org/ntlab/traceDebugger/analyzerProvider/DeltaExtractorJSON.java
index 944edf6..9e9e56e 100644
--- a/src/org/ntlab/traceDebugger/analyzerProvider/DeltaExtractorJSON.java
+++ b/src/org/ntlab/traceDebugger/analyzerProvider/DeltaExtractorJSON.java
@@ -120,13 +120,13 @@
 										
 					if (ownerObjectId.equals(thisObjectId)) {
 						// �t�B�[���h�Q�Ƃ̏ꍇ
-						removeList.add(refObjectId);
-						removeList.add(thisObjectId);		// ��ň�U�AthisObject ����菜��						
-						if (existsInFields == 0) {
+						if (!removeList.contains(refObjectId)) {
 							// ��ԋ߂��t�B�[���h�Q�Ƃ�D�悷��
+							removeList.add(refObjectId);
+							removeList.add(thisObjectId);		// ��ň�U�AthisObject ����菜��
 							aliasList.put(refObjectId, new Alias(Alias.AliasType.FIELD, 0, refObjectId, tracePoint.duplicate()));
+							existsInFields++;					// set�������get�����o���Ă���”\��������
 						}
-						existsInFields++;					// set�������get�����o���Ă���”\��������
 					} else {
 						// ���ڎQ�Ƃ̏ꍇ
 						boolean isSrcSideChanged = false;
diff --git a/src/org/ntlab/traceDebugger/analyzerProvider/DeltaMarkerManager.java b/src/org/ntlab/traceDebugger/analyzerProvider/DeltaMarkerManager.java
index f4e5890..532ee52 100644
--- a/src/org/ntlab/traceDebugger/analyzerProvider/DeltaMarkerManager.java
+++ b/src/org/ntlab/traceDebugger/analyzerProvider/DeltaMarkerManager.java
@@ -802,7 +802,6 @@
 					final MethodInvocation mi = (MethodInvocation)statement;
 					final MethodExecution calledMe = mi.getCalledMethodExecution();
 					final int index = alias.getIndex();
-					calledMe.getArguments().get(alias.getIndex());
 					visitor = new MyASTVisitor() {
 						@Override
 						public boolean visit(org.eclipse.jdt.core.dom.MethodInvocation node) {