An on-vehicle electronic control device improves safety so as to prevent an unnecessary start by means of an arousal timer circuit section. An on-vehicle electronic control device includes a main control circuit section and an arousal timer circuit section. A switching element is held in a closed-circuit operation with an output permitting signal that a watchdog timer circuit generates when a pulse cycle of a watchdog clear signal that a main CPU generates is normal, and thereafter an arousal output is reset in response to a forced OFF command from the main CPU. In the event that an arousal output is not reset, the arousal timer circuit section self-resets an arousal output after a predetermined time period has passed.