A traction control system for driving wheels of a vehicle, comprising: a power source; a starting clutch having a variable transmission torque capacity and interposed between the power source and the driving wheels (RR, RF, LR, LF) to connect and disconnect the power source and the driving wheels (RR, RF, LR, LF); a braking device associated with each of the driving wheels (RR, RF, LR, LF) and capable of independently controlling a braking force to each wheel; and a controller configured to lower a driving force transmitted from the driving wheels (RR, RF, LR, LF) to a road surface by controlling a driving torque of the power source and/or a braking force to the driving wheels (RR, RF, LR, LF) when an acceleration slip in the driving wheels (RR, RF, LR, LF) is above a certain value and further configured to reduce a lowering quantity of the driving force as the variable transmission torque capacity of the starting clutch decreases, wherein the power source includes an engine and a motor disposed at a power output side of the engine; the traction control system includes an engine clutch for connecting and disconnecting the engine and the motor; the starting clutch is interposed between the motor and the driving wheels (RR, RF, LR, LF); characterized in that the controller is further configured to set the lowering quantity of the driving force according to the variable transmission torque capacity of the starting clutch and a transmission torque capacity of the engine clutch, and the controller is further configured to set the lowering quantity of the driving force regardless of the transmission torque capacity of the engine clutch when the starting clutch is slip-engaged. a power source; a starting clutch having a variable transmission torque capacity and interposed between the power source and the driving wheels (RR, RF, LR, LF) to connect and disconnect the power source and the driving wheels (RR, RF, LR, LF); a braking device associated with each of the driving wheels (RR, RF, LR, LF) and capable of independently controlling a braking force to each wheel; and a controller configured to lower a driving force transmitted from the driving wheels (RR, RF, LR, LF) to a road surface by controlling a driving torque of the power source and/or a braking force to the driving wheels (RR, RF, LR, LF) when an acceleration slip in the driving wheels (RR, RF, LR, LF) is above a certain value and further configured to reduce a lowering quantity of the driving force as the variable transmission torque capacity of the starting clutch decreases, wherein the power source includes an engine and a motor disposed at a power output side of the engine; the traction control system includes an engine clutch for connecting and disconnecting the engine and the motor; the starting clutch is interposed between the motor and the driving wheels (RR, RF, LR, LF); characterized in that the controller is further configured to set the lowering quantity of the driving force according to the variable transmission torque capacity of the starting clutch and a transmission torque capacity of the engine clutch, and the controller is further configured to set the lowering quantity of the driving force regardless of the transmission torque capacity of the engine clutch when the starting clutch is slip-engaged.