diff --git a/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/TraceJSON.java b/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/TraceJSON.java
index 7a5037c..5161799 100644
--- a/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/TraceJSON.java
+++ b/org.ntlab.traceCollector/src/org/ntlab/traceCollector/tracer/trace/TraceJSON.java
@@ -1028,7 +1028,10 @@
 				for (int j = 0; j < args.size(); j++) {
 					startAliasList.add(new Alias(args.get(j).getId(), tp, (j + Alias.OCCURRENCE_EXP_FIRST_ARG)));
 				}
-				startAliasList.add(new Alias(calledMe.getReturnValue().getId(), tp, Alias.OCCURRENCE_EXP_RETURN));
+				ObjectReference returnValue = calledMe.getReturnValue();
+				if (returnValue != null) {
+					startAliasList.add(new Alias(returnValue.getId(), tp, Alias.OCCURRENCE_EXP_RETURN));
+				}
 			}
 		}
 		return startAliasList;
@@ -1046,15 +1049,15 @@
 		String objId = startAlias.getObjectId();
 		TracePoint tp = startAlias.getOccurrencePoint().duplicate();
 		ArrayList<ArrayList<Alias>> resultLists = getObjectFlow(aliasLists, objId, tp, 0);
-		for (int i = 0; i < resultLists.size(); i++) {
-			ArrayList<Alias> resultList = resultLists.get(i);
-			System.out.println("---------------------------------------------------------");		// �m�F�p
-			for (Alias alias : resultList) System.out.println(alias);								// �m�F�p
+//		for (int i = 0; i < resultLists.size(); i++) {
+//			ArrayList<Alias> resultList = resultLists.get(i);
+//			System.out.println("---------------------------------------------------------");		// �m�F�p
+//			for (Alias alias : resultList) System.out.println(alias);								// �m�F�p
 //			int lastAliasOccurrenceEXP = resultList.get(resultList.size() - 1).getOccurrenceExp();
 //			if (lastAliasOccurrenceEXP != Alias.OCCURRENCE_EXP_RETURN) {
 //				resultLists.remove(resultList); // �����̃G�C���A�X���z�񐶐���R���X�g���N�^�Ăяo���ł͂Ȃ����X�g���폜����
 //			}
-		}
+//		}
 		return resultLists;
 	}
 
@@ -1099,7 +1102,6 @@
 					// �߂�l�ɃG�C���A�X�̃I�u�W�F�N�gID����v�����ꍇ
 					aliasList.add(new Alias(objId, tp.duplicate(), Alias.OCCURRENCE_EXP_RETURN));
 					if (calledMethodExecution.isConstructor()) {
-						System.out.println("return (Constructor)");
 						return aliasLists; // �R���X�g���N�^�Ăяo���ӏ��̓G�C���A�X�̋N���Ȃ̂ł���ȑO�ɂ͂����Ȃ��͂�
 					}
 					TracePoint exitTp = calledMethodExecution.getExitPoint(); // �Ăяo�����\�b�h���s�̍ŏI�X�e�[�g�����g���w��tp���擾