The connector reception portion is configured such that, when the battery pack is housed in the battery housing portion, the battery cylindrical portion is positioned at the connector reception portion of the battery housing portion, and thereafter, while the battery pack is inclined so that the battery cylindrical portion is located diagonally forward down with respect to the battery mounting surface, the battery cylindrical portion is inserted and fitted within the peripheral wall of the connector reception portion, and the battery pack is inclined so that an inclination angle is smaller while the battery pack is pushed forward in this fitted-and-inserted state, thereby the battery pack is laid on the battery mounting surface of the battery housing portion, and the battery connector is connected to the connection terminals in a direction parallel to the battery mounting surface.