PURPOSE: To prevent an one-sided loading state of load by calculating and displaying the loading state of the load frame vehicle height data detected by a vehicle height detecting sensor fitted to each wheel.

CONSTITUTION: The vehicle height detecting sensors 1W4 are arranged respectively to respective right and left wheels FR, FL, RR, RL of front wheels (F) and rear wheels (R). Then, outputs of the respective vehicle height sensors 1W4 are taken in a microprocessor 5 and a load balance of the wheels before and behind and right and left is calculated there and displayed on a display part 6. Accordingly, since the loading state of the load can be recognized at a glance by display of the display part 6, the one-sided loading state of the load can be prevented.