1. A virtual computer system comprising: a first saving unit that saves at least one or more snapshots each having recorded therein a state of a virtual machine, the state including an application program installed on the virtual machine, the snapshot being saved as a reference snapshot; an applying unit that applies the reference snapshot to the virtual machine when an execution request for the application program is received; and a second saving unit that saves a state of the virtual machine that executes the application program, the state being saved as a snapshot.