It is determined whether an arithmetic operation function of a device to be inspected is normal or not. A MCU 13 to be inspected acquires a constant to be used for an arithmetic problem from a power source IC 12 on an inspection side. The MCU 13 sequentially selects a plurality of the arithmetic problems and carries out an arithmetic operation using the acquired constant according to the selected arithmetic problem. A monitoring circuit 23 of the power source IC 12 receives the result of the arithmetic operation of the arithmetic problem from the MCU 13. The monitoring circuit 23 compares the received arithmetic operation result with the arithmetic operation result of the arithmetic problem calculated at the side of the monitoring circuit 23. The monitoring circuit 23 determines whether the arithmetic operation function of the MCU 13 works normally or not based on the comparison result.