An ECU controls a starter relay. Output angle detector detects a rotational angle of an output shaft in a rotary actuator. The ECU stores a first rotational angle which is detected by the output angle detector when a starting switch is OFF. When the starting switch is ON and when the difference between a second rotational angle detected at that time by the output angle detector and the first rotational angle already stored is not within a certain value, the ECU inhibits the operation of the starter relay to inhibit engine start.