The present invention provides a motor drive control device provided with a shutoff circuit employing semiconductor relays and configured to drive a motor by a duty ratio control of an inverter, which stably drives the motor even in an operation state that drive duty ratio of phases are uneven. In the motor drive control device, output lines of three phases of the inverter circuit are connected to phases of the motor and further connected to a booster circuit, an output boosted by the booster circuit at a time of drive of the motor is distributed to semiconductor relays connected to respective phases of the motor, and furthermore, a switching circuit for stopping actuation of the booster circuit to shut off drive of the motor, is interposed in a line for supplying an electric power to the booster circuit.