A motor drive device employed, for example, in an electric power steering apparatus for vehicle, achieves a reduction not only in size but also in vibration and noise at the same time.At least one of a motor drive control unit (30) and a motor (10) is provided with at least two screw holes (53) for fixation to a gear (speed reducer) of an electric power steering apparatus. Let L1 be a maximum value of a distance between center points of the screw holes (53) and L2 be a distance between an end face (D) of a stator iron core (12) in an axial direction on a farther side from the gear and an attachment surface (C) attached to a gear side, then a value of L1 is equal to or greater than a value of L2.