1. A computer system which handles web requests received from clients, comprising: a request classification log generating tool generating a request classification log which describes a number of web requests handled by said computer system in each measurement period for each type of said web requests; a system log generating tool generating a system log which describes a status of resources of said computer system in said each measurement period; and a resource usage status calculation tool calculating a request handling resource usage amount per web request by using said request classification log and said system log for each type of said web requests, the request handling resource usage amount being a usage amount of resources used for handling said web requests