PURPOSE: To control a self-system power source and other power sources without operating a switch by combining plural computer systems so as to attain a power source control system which turns on and off the power sources and rendering a system power source control part to receive a power source turning- off instruction signal from one system and power source turning-off instruction signals from the other systems through different routes.

CONSTITUTION: It is assumed that where systems #0 and #1 are master and slave, the system power source turning-off instruction signal is given from a console CSL#0 30-0 after an entire system changes to a partition structure from a multistructure. The signal is transmitted as follows: CSL#0→IPC#0→line l3→SPC#0. The system #0 in a #0 system power controller 330 is discriminated whether it is of the partition structure, and according to the power source turning-off instruction signal, all power sources 37-1W37-n and 43-1W43-m are turned off. On the other hand the power source turning-off signal from the console 30-0 is transmitted to a #1 system power controller 340. However, an internal service processor discriminates that the system #1 is of the partition structure, neglects the power source turning-off instructions from the other systems and continues operating the system #1.