Abstract: A regenerative braking controller for use with a series-wound DC motor which drives an electric car for railways or electric automobile and which is controlled by a thyristor chopper comprises a series-connected circuit including an armature of the DC motor, a field winding thereof and a smoothing reactor, a chopper connected in parallel with said series-circuit, a diode connected between said parallel circuit and a power supply, and a gate controller for applying a gate signal to said chopper in succession only during a period of time when said chopper is to be rendered conductive.