A regenerative braking system has a generator connected to at least one wheel set to apply regenerative brake torque to it by generating electricity, a regenerative braking control means controlling a regenerative braking amount, an actual wheel speed variation calculating means calculating an actual wheel speed variation between actual outer-wheel speed of an outer wheel of steerable wheels and actual inner-wheel speed of at least one wheel of front and rear wheel sets, a correspondent wheel speed variation calculating means calculating a correspondent wheel speed variation corresponding to an outer-to-inner wheel speed variation of the steerable wheels with road grip, a steer characteristic judging means judging strength of a steer characteristic based on the correspondent wheel speed variation and the actual wheel speed variation, and a regenerative braking amount compensating means compensating the amount to be more decreased as the steer characteristic becomes stronger.