A traction control system comprises a detector configured to detect a monitored spin value corresponding to a spin amount of a drive wheel in a vehicle; a condition determiner configured to determine whether or not the monitored spin value detected by the detector meets a driving power suppressing condition; and a controller configured to execute a traction control for reducing a driving power of the drive wheel based on the determination; the condition determiner being configured to set the driving power suppressing condition variably based on at least one of a variable parameter relating to a rotation number difference which is variable according to a change rate of a rotation number difference between the drive wheel and a driven wheel, and a variable parameter relating to rotation of a drive system which is variable according to a rotation change rate of the drive system for driving the drive wheel.