PURPOSE: To rapidly carry out horizontal control of a car body by correcting the car height so as to keep the prescribed standard value of the average height for left and right crawlers when the aforementioned average height is lowered to the above-mentioned standard value or below.

CONSTITUTION: The average height H1=(L1+R1)/2 is determined from the standard height (L1) on the left side of a car body 1 and the standard height (R1) on the right side. The height on the left side is changed to L2 in tilting the car body 1 by a tilt lever switch and the height on the right side is changed to R2. If the lowering speed of one thereof is higher than that of the other at this time, the average height is as follows; (L1+R1)/2>(L2+R2)/2 and is lower than that of the standard value. In this case, the car height is corrected by a height (α) satisfying the formula [(L2+α)+(R2+α)]/2=(L1+R1)/2 with a car height correcting device in a controller.