The monitoring technology capable of reducing total monitoring cost without degrading the monitoring capability in accordance with the configuration of the large-scale service system and quickly comprehending the state of the service system after the configuration change. A monitoring system in which information processing apparatuses constituting the service system are objects to be monitored has a monitoring manager program and a plurality of monitoring agent programs, and objects to be monitored having the same performance characteristics are sorted into the same groups. In each of the groups, parties where monitoring is carried out at a short monitoring interval and parties where the monitoring is carried out at a long monitoring interval are provided. The performance of objects to be monitored in the party of the long monitoring interval is estimated from the performance of the objects to be monitored in the party of the short monitoring interval.