In a planetary gear device, a first side plate as carrier is formed to a disc plate shape and secures thereto pins to protrude the pins from one end surface in an axial direction. The outside diameter of the first side plate is formed to be a small diameter on one side in the axial direction and a large diameter on the other side in the axial direction. The first side plate is provided with press-fitting hole portions with the pins press-fitted thereinto and small-diameter side concavities that are formed on the press-fitting hole portions on one side in the axial direction, that open to one end surface in the axial direction of the first side plate and that have internal surfaces being out of contact with the pins at at least parts thereof.