A cam plate is coupled to a driven-side shaft and is rotatable relative to a housing. A gear is placed on a side of the cam plate, which is opposite to the driven-side shaft. The housing has a contact surface that is configured to contact a wall surface of the cam plate, which is located on one side in an axial direction of the housing. Among two external toothed portions, one external toothed portion is located on an opposite side of the contact surface, which is opposite to the gear in the axial direction. The cam plate has a bearing portion that is located on a side of the contact surface, which is opposite to the gear, and the bearing portion has an outer peripheral surface configured to receive a radial load applied from an inner peripheral surface of the housing in a radially inward direction.