A configuration information collection unit 1502 and a transaction collection unit 1503 collect a transaction as the configuration information about an IT system and communication data, and stores them in a CMDB 1504. A multiplexed application detection unit 1501 detects as a candidate for a multiplexed application the software of applications multiplexed by evaluating whether or not the application names of the software of applications deployed to a target to be monitored on the IT system match each other. Then, it detects a multiplexed application by evaluating whether or not one or more of evaluation items of a subnet in which a candidate for a multiplexed application is performed, transaction context as the data relating to the names of an applications performed before and after the candidate for a multiplexed application, and transaction information as the transmission/reception data of the candidate for a multiplexed application match each other.