A wheel slip controlling system is provided to immediately control the rotation of the drive wheels by controlling the output power of an internal combustion engine as well as by controlling the brake mechanism of the drive wheels when a slippage is detected during the process of braking or acceleration. The brake mechanism is an anti-skid control system which uses a pressure change-over valve to accurately control the braking force. The wheel slip controlling system also includes a second throttle valve responsive to a traction control mechanism for controlling the amount of intake air of the internal combustion engine such that the speed of the driven wheels can be slowed when slipping occurs.
