An in-wheel motor drive device includes a motor part, a speed reducer part, a wheel bearing part, a casing, and a lubrication mechanism configured to supply lubricating oil to the motor and speed reducer parts. A rotation shaft of a motor in the motor part is configured to drive an input shaft of a speed reducer having eccentric portions to rotate. The speed reducer part reduces a speed of rotation of the input shaft of the speed reducer and transmits the rotation to an output shaft of the speed reducer. The wheel bearing part is connected to the output shaft of the speed reducer. The motor part includes a stator fixed to the casing and a rotor arranged at the rotation shaft of the motor. A shielding plate that reduces stirring resistance of the lubricating oil generated by rotation of the rotor is arranged in the motor part.