1. A computational resource assignment device in a multi-core processor system, said multi-core processor system comprising: a plurality of processors; and a plurality of cache memories respectively utilized by said plurality of processors, said computational resource assignment device comprising: an assignment management unit configured to manage assignment of tasks to said plurality of processors; and a cache status calculation unit configured to calculate a cache usage status with respect to each of said tasks, wherein said cache usage status includes at least one of a memory access count and a cache hit ratio, wherein said plurality of processors includes: a first processor handling a plurality of first tasks that belong to a first process; and a second processor handling a second process that is different from said first process, wherein if computation amount of said first process exceeds a predetermined threshold value, said assignment management unit refers to said cache usage status calculated with respect to each of said tasks to preferentially select, as a migration target task, one of said plurality of first tasks whose said memory access count is smaller or whose said cache hit ratio is higher, and newly assigns said migration target task to said second processor.