PURPOSE: To constitute so that any computer can be stopped causing no inconsistency, by executing a unified control by synchronizing with each other, to plural independent computers coupled by an inter-channel coupling device.

CONSTITUTION: When a stop request is instructed from a console device 1, a stop processing task 3 transmits stop commands 11, 11' to all other subcomputers 4, 4', and starts stop processing tasks 6, 6'. The stop processing tasks 6, 6' checks a direct access storage device DASD 7 which is used in common between plural computers, and monitors an occupied state of the DASD 7 at a constant time interval. In this state, only when the occupied state of all DASDs is released within a fixed time, the stop processing of a processor is continued, and in case when an unreleased DASD exists, the stop processing is suspended. In this case, a new request to the DASD is all set to a waiting state.