Provided is a motor drive device (1) comprising: a trailing arm (2) which extends in the front-rear direction of a vehicle, has formed on the front side thereof a vehicle body-side mounting section (6) connecting to the vehicle body through a rubber bush (5), and has formed on the rear side thereof a wheel-side support section (7) for supporting a rear wheel (71); and a motor (3) supported by thetrailing arm (2) and driving the rear wheel (71). The motor drive device (1) is characterized in that, when viewed in the vehicle width direction, the motor (3) is installed at a position overlappingthe rubber bush (5) in the vertical direction of the vehicle.