PURPOSE: To obtain a means which dynamically selects a representative processor module PM of a computer system, which is provided with plural PMs having several central processing units and memories, after the start of the system.

CONSTITUTION: An area 13 where the identifier of the representative PM is stored is provided on a PM shared memory 12 shared among plural PMs, and each PM tries to set its own identifier to the area 13 based on the exclusive processing, and only the identifier of the PM which first tries to set its own identifier is written in the area 13, and the PM of the identifier written in the area 13 is selected as the representative PM.