PURPOSE: To execute a check of an analog signal outputting circuit at high speed by providing a converting circuit having the same constitution as that of the analog signal outputting circuit, and comparing an output from the converting circuit with an output from the analog signal outputting circuit.

CONSTITUTION: Parallel signals 23A, 23B,... from a microprocessor 20 are changed to pulse outputs 1A, 1B,... whose pulse width has been modulated by pulse width modulating circuits 21A, 21B,..., and in order to execute a check of voltage or current signals 5A, 5B,... by a pulse width/voltage or current converting circuit 22, the signal 23N is sent successively to the circuit 21N, and whether it is large or small is compared by comparators 6A, 6B,.... Its result is inputted to a processor 20 as outputs 7A, 7B,... of the comparators 6A, 6B,..., and by the magnitude relation of the signals 5A, 5B,... and a comparing signal 11, a check of an outputting circuit can be executed. Also, by setting a time constant of a filter 9 of a generating circuit of the signal 11 to a small value, the check can be executed at a high speed.