Provided is a computer system, in which a storage system includes a first control module for logically dividing first resources of the storage system and operating them as independent virtual storage systems. A computer includes a second control module for logically dividing second resources of the computer and operating them as independent virtual machines. The computer system holds first information indicating a correlation among the virtual machine, the virtual storage system, and the first resources. The first control module specifies the first resource allocated to the virtual storage system whose power is cut based on the first information, and powers off the specified first resource. Thus, system power consumption can be reduced by managing power of the storage system shared by a plurality of virtual machines in a virtualization environment.