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());