diff --git a/sakura_core/mem/CMemory.cpp b/sakura_core/mem/CMemory.cpp
index 0916447a16..e4f82c55a4 100644
--- a/sakura_core/mem/CMemory.cpp
+++ b/sakura_core/mem/CMemory.cpp
@@ -312,10 +312,6 @@ void CMemory::AllocBuffer( int nNewDataLen )
 	}else{
 		/* ���݂̃o�b�t�@�T�C�Y���傫���Ȃ����ꍇ�̂ݍĊm�ۂ��� */
 		if( m_nDataBufSize < nWorkLen ){
-			// �p�ɂȍĊm�ۂ��s��Ȃ��悤�ɂ���ׁA�K�v�ʂ̔{�̃T�C�Y���m�ۂ���
-			if (nWorkLen < std::numeric_limits<int>::max() / 2) {
-				nWorkLen *= 2;
-			}
 			// 2014.06.25 �L���f�[�^����0�̏ꍇ��free & malloc
 			if( m_nRawLen == 0 ){
 				free( m_pRawData );
@@ -399,7 +395,7 @@ void CMemory::SetRawDataHoldBuffer( const CMemory& pcmemData )
 void CMemory::AppendRawData( const void* pData, int nDataLenBytes )
 {
 	if(nDataLenBytes<=0)return;
-	AllocBuffer( m_nRawLen + nDataLenBytes );
+	_ReallocIfNeeded( nDataLenBytes );
 	_AddData( pData, nDataLenBytes );
 }
 
@@ -412,7 +408,7 @@ void CMemory::AppendRawData( const CMemory* pcmemData )
 	}
 	int	nDataLen;
 	const void*	pData = pcmemData->GetRawPtr( &nDataLen );
-	AllocBuffer( m_nRawLen + nDataLen );
+	_ReallocIfNeeded( nDataLen );
 	_AddData( pData, nDataLen );
 }
 
@@ -425,12 +421,10 @@ void CMemory::_Empty( void )
 	return;
 }
 
-
-
 void CMemory::_AppendSz(const char* str)
 {
 	int len=strlen(str);
-	AllocBuffer( m_nRawLen + len );
+	_ReallocIfNeeded(len);
 	_AddData(str,len);
 }
 
@@ -443,3 +437,15 @@ void CMemory::_SetRawLength(int nLength)
 	m_pRawData[m_nRawLen  ]=0;
 	m_pRawData[m_nRawLen+1]=0; //�I�['\0'��2�•t������('\0''\0'==L'\0')�B
 }
+
+void CMemory::_ReallocIfNeeded(int appendLength)
+{
+	assert(appendLength >= 0);
+	if(m_nDataBufSize - 2 - m_nRawLen < appendLength) {
+		int64_t newSize1 = (int64_t)m_nRawLen + 2 + appendLength;
+		int64_t newSize2 = (int64_t)m_nDataBufSize * 2;
+		int64_t newSize = std::min(std::max(newSize1, newSize2), (int64_t)std::numeric_limits<int>::max());
+		AllocBuffer( (int)newSize );
+	}
+}
+
diff --git a/sakura_core/mem/CMemory.h b/sakura_core/mem/CMemory.h
index 6e39ec0101..65e0024441 100644
--- a/sakura_core/mem/CMemory.h
+++ b/sakura_core/mem/CMemory.h
@@ -87,6 +87,7 @@ class CMemory
 	*/
 	void _Empty( void ); //!< �������Bm_pRawData��NULL�ɂȂ�B
 	void _AddData( const void*, int );
+	void _ReallocIfNeeded(int appendLength);
 public:
 	void _AppendSz(const char* str);
 	void _SetRawLength(int nLength);