When a gearshift of a vehicle is in drive, a video image of a movement state of the vehicle moving forward depending on the rotation of the wheels detected by a wheel rotation sensor is displayed on a monitor. Thereafter, when the gearshift is in neutral, a video image of a movement state of the vehicle moving forward depending on the rotation of the wheels is displayed on the monitor. When the gearshift is in rear where the vehicle moves in a second direction opposite to a first direction, a video image of a movement state of the vehicle moving in the second direction depending on the rotation of the wheels is displayed on the monitor. Thereafter, when the gearshift is in neutral, a video image of a movement state of the vehicle moving in the second direction depending on the rotation of the wheels is displayed on the monitor.