A traction control system for a vehicle reduces the rate of slip of driving wheels of the vehicle by reducing the traction force transmitted to the road surface from the driving wheels when the driving wheels slip. Whether the vehicle is making a turn is judged, and whether the vehicle is in an instable state which occurs when the vehicle is making a turn. The traction force is reduced by a higher rate when the driving wheels slip while the vehicle is making a turn than when the driving wheels slip while the vehicle is running straight, and the traction force is reduced by a higher rate when the driving wheels slip while the vehicle is in an instable state than when the driving wheels slip while the vehicle is making a turn.