PURPOSE: To provide a memory check method capable of performing check even while a program is being executed in a program down-loading type device.

CONSTITUTION: When the check of memory is performed after a memory check instruction which checks the memory on which a prescribed program is down- loaded, the execution of the program written on the memory, and the result of execution of the program is processed, it is judged whether or not the memory is accessed in he regulated number of times when the memory check instruction is issued while the program is being executed, and arithmetic processing in accordance with access for one address of the memory is repeated by the regulated number of times, and when it is judged that the access is performed by the memory check instruction in the regulated number of times, the batch check of a computed result by the memory check instruction can be performed.