To improve the efficiency of paging by deciding a page in use to perform page-out based on the regular pattern of the order of the page to be used when a page fault is generated.

When the execution of a program is started, the number of the page to be accessed is registered in an access page history storage part 5 and registered in an LRU(least recently used) management storage part 4 as a priority order '1'. Thereafter, a similar processing 15 performed every time the page to be accessed is switched, and when the accessed page is accessed again after several pages, a history during the time is extracted from the access page history storage part 5 and registered in an access page pattern storage part 6 as pattern data. When the page fault is generated, the pattern data for the page to be accessed are read and a paging processing is performed with the page not present in the pattern as a page-out object.