diff --git a/src/main/java/com/eactive/eai/common/logger/EAIFileLogger.java b/src/main/java/com/eactive/eai/common/logger/EAIFileLogger.java
index e665082..7451a72 100644
--- a/src/main/java/com/eactive/eai/common/logger/EAIFileLogger.java
+++ b/src/main/java/com/eactive/eai/common/logger/EAIFileLogger.java
@@ -717,7 +717,8 @@ public class EAIFileLogger
             sb.appendAndDelimeter( NullControl.addSpace(message.getRspnsChngMsgType()));   // 응답변환유형
 
             // log level 'E' or 'F'
-            if ("E".equals(logRspErrCd.substring(1, 2)) || "F".equals(logRspErrCd.substring(1, 2))) {
+            String logErrLvl = StringUtils.substring(logRspErrCd, 1, 2);
+            if ("E".equals(logErrLvl) || "F".equals(logErrLvl)) {
                 sb.appendAndDelimeter( NullControl.addSpace(logRspErrCd)); //EAI에러코드
                 sb.appendAndDelimeter( StringUtil.chunkString(message.getRspErrMsg(),1000)); //EAI에러내용
             }
diff --git a/src/main/java/com/eactive/eai/common/logger/EAILogDAO.java b/src/main/java/com/eactive/eai/common/logger/EAILogDAO.java
index 6130554..902e63f 100644
--- a/src/main/java/com/eactive/eai/common/logger/EAILogDAO.java
+++ b/src/main/java/com/eactive/eai/common/logger/EAILogDAO.java
@@ -661,8 +661,8 @@ public class EAILogDAO {
 			eaiLog.setRspnschngmsgtype(message.getRspnsChngMsgType());
 
 			// log level 'E' or 'F'
-			if ("E".equals(logRspErrCd.substring(1, 2))
-					|| "F".equals(logRspErrCd.substring(1, 2))) {
+			String logErrLvl = StringUtils.substring(logRspErrCd, 1, 2);
+			if ("E".equals(logErrLvl) || "F".equals(logErrLvl)) {
 				// EAI에러코드
 				eaiLog.setEaierrcd(logRspErrCd);
 				// EAI에러내용
@@ -770,8 +770,8 @@ public class EAILogDAO {
 			// 수동시스템어댑터업무그룹명
 			eaiErrorLog.setPsvsysadptrbzwkgroupname(message.getCurrentSvcMsg().getPsvSysItfTp());
 
-			if ("E".equals(logRspErrCd.substring(1, 2))
-					|| "F".equals(logRspErrCd.substring(1, 2))) {
+			String logErrLvl = StringUtils.substring(logRspErrCd, 1, 2);
+			if ("E".equals(logErrLvl) || "F".equals(logErrLvl)) {
 				// EAI에러코드
 				eaiErrorLog.setEaierrcd(logRspErrCd);
 				// EAI에러내용
diff --git a/src/main/java/com/eactive/eai/common/monitor/EAIServiceMonitor.java b/src/main/java/com/eactive/eai/common/monitor/EAIServiceMonitor.java
index f8342c1..37310a1 100644
--- a/src/main/java/com/eactive/eai/common/monitor/EAIServiceMonitor.java
+++ b/src/main/java/com/eactive/eai/common/monitor/EAIServiceMonitor.java
@@ -292,7 +292,7 @@ public class EAIServiceMonitor implements Lifecycle {
 			msgPssTm = msg.getMsgPssTm();
 			msgRcvTm = msg.getMsgRcvTm();
 			logPssSno = msg.getLogPssSno();
-			rspErrCd = msg.getLogRspErrCd();
+			rspErrCd = StringUtils.defaultString(msg.getLogRspErrCd());
 			eaiSvcCd = msg.getEAISvcCd();
 			svcOgNo = msg.getSvcOgNo();
 			bwkCls = msg.getBwkCls();
@@ -317,7 +317,7 @@ public class EAIServiceMonitor implements Lifecycle {
 				error = rspErrCd.substring(1, 2);
 			}
 			
-			if (rspErrCd.equals("RECEAIINA001")) {
+			if ("RECEAIINA001".equals(rspErrCd)) {
 				error = "S";
 			}
 
@@ -326,7 +326,8 @@ public class EAIServiceMonitor implements Lifecycle {
 				iErrorCode = 1;
 
 				// Timeout
-				if (timeOutCodes.indexOf(rspErrCd) > 0) {
+				// 목록 첫 번째 코드는 indexOf 가 0 이므로 '> 0' 이면 매칭되지 않는다. (isTimeOutCodes() 와 동일하게 '>= 0')
+				if (timeOutCodes.indexOf(rspErrCd) >= 0) {
 					iErrorCode = 2;
 				}
 				// 업무에러코드에 없을 경우 통신(시스템)에러로 처리함