PURPOSE: To make abnormal accelerating slip control hard to be performed by correcting the reference speed of a driving wheel so as to be relatively increased to the detected speed at a time when duration checking rotation of the driving wheel has come to more than the reference time.

CONSTITUTION: Speed of a car body is detected by a means A, while speed of a driving wheel is detected by a means B. Then, on the basis of the detected speed of the car body, reference speed of the driving wheel is determined by a means C. In addition, when the detected speed of the driving wheel is more than the reference speed, rotation of the driving wheel is controlled, while this rotation is controlled by a means D so as to allow it if a specified condition is satisfied. In this case, duration when the rotation of the driving wheel is checked is detected by a means E. If this duration is more than the reference time, the reference speed of the driving wheel is corrected by a means F so as to be relatively increased to the detected speed. With this constitution, after correction, abnormal accelerating slip control is made hard to be performed, thereby checking any drop in accelerability.