According to an aspect of the embodiment, a host virtual machine operated on the CPU controls the virtual machine system and a guest virtual machine, and has save information of system information which defines a save location to save the system information of the guest virtual machine. The save location is in the storage device used by the host virtual machine. A virtual machine monitor operated on the CPU controls the plurality of virtual machines, and includes monitoring unit which monitors the guest virtual machine to detect occurrence of a failure in the guest virtual machine, and collecting unit which collects the system information from the save location based on the save information of system information when the monitoring unit detects the failure in the guest virtual machine.