A searching order control portion has a searching order table for a memory pool having sub-memory pools. The searching order table has entries in which request memory area size ranges and corresponding searching orders are entered. The searching order control portion finds the sub-memory pool that should be searched for an assignable memory area by the use of the searching order table in response to a request of a getting request receiving portion. The searching order control portion notifies a sub-memory pool ID of the found sub-memory pool to the getting request receiving portion. The getting request receiving portion makes a getting portion try getting a memory area with request memory area size from the sub-memory pool of the sub-memory pool ID. The getting request receiving portion repeats the above-mentioned operation until the getting portion gets the memory area or the searching order control portion notifies the end of search.