When the boot monitoring unit receives, from a management server, a first boot response for a first boot request from a NIC1 of a managed server, a boot monitoring unit stores a receiving time of the first boot response. When the boot monitoring unit receives a second boot request from a NIC2 of the managed server, and when a predetermined time has not elapsed from the receiving time, the boot monitoring unit determines that the management server is normal, and transmits an NOP program to the managed server. When the predetermined time has elapsed from the receiving time, the boot monitoring unit determines that the management server is stopped, and transmits a recovering program to the managed server.