A steering angle of steered wheels and a vehicle speed of a fork-lift truck are respectively detected by sensors (4, 5). A CPU (1) compares the vehicle speed with a predetermined speed (S2), and causes a meter (6) to display the steering angle when the vehicle speed is lower than the predetermined speed (S4, S14), and causes the meter (6) to display the vehicle speed when the vehicle speed not lower than the predetermined speed (S3, S13). As a result, the space for the display device can be reduced without affecting the operation efficiency of the fork-lift truck.