If a turn signal switch is operated and a right-turn signal or a left-turn signal is input, a turn signal controller outputs a turn signal lamp lighting signal to a relay so as to make the turn signal lamp flash. Detection signals of an operating amount and an operating direction of a joy stick are input to a main controller, and the main controller detects a steering angle of the vehicle on the basis of the input detection signals, and outputs the steering angle to the turn signal controller. The turn signal controller determines that a course change is finished in a case the input steering angle becomes smaller than a second steering angle after becoming larger than a first steering angle, and stops a turn signal lamp lighting signal on an output state so as to turn off a flashing turn signal lamp.