A VMM disables an interrupt interception flag on at least one CPU to execute, upon reception of an interrupt, an interrupt handler code of an OS, and enables the interrupt interception flag on the at least one CPU to execute, upon the reception of the interrupt, an emulator in the VMM. When, to a virtual machine, an I/O device is assigned in a dedicated form, and when the CPU is assigned while the interrupt interception is disabled, a destination of the interrupt from the physical I/O device is set to the corresponding CPU on which the interrupt interception is disabled. When, to the virtual machine, the I/O device is assigned in a shared form, or when the CPU is assigned while the interrupt interception is disabled, the destination of the interrupt from the physical I/O device is set to the corresponding CPU on which the interrupt interception is enabled.