PURPOSE: To improve the hit rate of a cache memory in a load decentralized OS.

CONSTITUTION: In a function decentralization system of a cache memory secures the coincidence of contents between the cache memory and a main storage of a multiprocessor system using a memory sharing system for each processor based on the state display of each cache memory. When a transfer request of a memory block is produced by a writing mistake of a cache memory, a bus request is produced for transfer of the memory block and also to simultaneously and forcibly read the memory block to be transferred to the processor that produced a memory block transfer request into the next practicable processor. This processor displays a state where the memory blocks to be transferred to the processors having the block transfer requests are simultaneously and forcibly read.