PURPOSE: To improve a fail safe function for traction control.

CONSTITUTION: A slip amount S of a drive wheel is calculated from a speed difference between a drive wheel and a driven wheel and acceleration XG of a vehicle from the speed change of a driven wheel at S1-S5. A throttle valve opening THR1 corresponding to engine torque necessary to acceleration is estimated. When a difference between the aforementioned throttle valve opening and a throttle valve opening THR2 detected from a throttle sensor is below a given value β, a reduction amount of a vehicle drive force is set as a function value f1 (S, THR2) of a slip amount S and the throttle valve opening THR2 and when it exceeds the given value β, a reduction amount of a vehicle drove force is set as a function value f2 (S) of only the slip amount S and throttle of a second throttle valve is controlled at S6-S13.