A reference value for a traction control is calculated based on a vehicle speed. When a vehicle is in a predetermined turning state, so that a driven wheel speed is equal to or lower than a predetermined value and a lateral acceleration is equal to or larger than a predetermined value, a correction value is searched from a table based on the vehicle speed and a steering angle to correct an error of the reference value generated due to a difference between the locus of the driven wheels and the locus of the follower wheels during turning of the vehicle. The reference value is corrected by subtracting the correction value from the reference value (when the vehicle is a rear wheel drive vehicle) or by adding the correction value to the reference value (when the vehicle is a front wheel drive vehicle. Thus, the reference value for the fraction control such as a reference value for a target slip rate can be accurately in accordance with the turning state of the vehicle.
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