PURPOSE: To prevent a roughly connected multiprocessor type computer system from being deteriorated in its performance by suppressing the generation of a disk access and suppressing also communication quantity on a system bus.

CONSTITUTION: A subsystem A15 consisting of a processing A151 is connected to a subsystem B 16 consisting of a processor B 161 through an exclusive inter- processor communication line 17 at the rate of 1 to 1 and inter-processor communication control devices A 155, B165 control the communication line 17. While executing communication between the processors A151, B161 through the communication line 17 by using the control devices A155, B165, respective interprocessor file sharing processing means A152, B162 store file cache copies in respective local memories A153, B163 of respective processors A151, B161 to control file sharing.