A circuit board includes a board body disposed on the opposite side of a plate-shaped portion of a center piece to a stator, and a heat generating element mounted to a surface on the plate-shaped portion side of the board body and disposed inside a radial direction range of a rotor housing. A heat-dissipation portion of a heatsink is on the plate-shaped portion side of the circuit board such that the heat-dissipation portion contacts the heat generating element either directly or through a thermally conductive material. A guide that opposes the heat-dissipation portion in an axial direction of a motor unit is formed at the plate-shaped portion. The guide forms an airflow guiding path between itself and the heat-dissipation portion, the airflow guiding path being shaped so as to guide air taken in through an air intake port from the radial direction outside toward a center of the motor unit.