The motor drive device includes: an electric motor (6); a controller (1) that controls a torque of the electric motor (6) or a quantity of state corresponding to the torque; and a torque transmitter that transmits the torque of the electric motor (6) to a wheel of a vehicle. The controller (1) includes a torque fluctuation inhibiting section (15) that inhibits torque fluctuation in the electric motor (6). The torque fluctuation inhibiting section (15) includes an execution determination section (15b) that determines whether or not to inhibit the torque fluctuation in the electric motor (6), based on a result of comparison between an estimated value of a torque fluctuation frequency in the electric motor (6), and one or both of transmission characteristics of the torque transmitter and vibration characteristics in the vehicle.