PURPOSE: To improve a function of stabilization for a traveling attitude of a car body, by detecting a surface gradient through each signal out of a level sensor and a tilt sensor, while controlling each of level-control mechanism so as to cause them to become a stable attitude to a road surface.

CONSTITUTION: When car levels 1W4, a sidewise tilt 5, a lengthwise tilt 6, a steering turning angle 7, a car speed 8 and a setting car level 9 are all inputted into a central processing unit 10, this CPU10 processes the steering turning angle 7 in accordance with the prescribed program and judges of whether car tilt control is necessary or not. If judging 'necessary', it determines a level-control value in each of level-control mechanisms 14W17 with these tilt angles 5 and 6, car levels 1W4, the steering turning angle absolute value 7 and the car speed 8 through operation of a surface tilt angle and a ground tilt angle by the prescribed program, thus the CPU10 outputs a regulating signal to each of these level-control mechanisms 14W17. With this constitution, a car body can be kept in its stable attitude even when a road surface is inclined.