A method for managing virtual machines, the method causing a management server having a database includes link relation information and connected to a plurality of physical servers, on which virtual machine hosts are installed, the method includes updating the link relation information in such a manner that a link between a virtual machine host and a first virtual machine guest is disconnected, when information regarding the first virtual machine guest cannot be acquired from the virtual machine host and updating the link relation information stored in such a manner that a link between a virtual machine host and a second virtual machine guest, when information regarding the second virtual machine guest is acquired from the virtual machine host.