Abstract: An AC generator slip ring device including a shaft supported by a front and rear bracket, and a rotor on the inner circumferential side of a stator; a sleeve fixed to an end portion on the rear bracket side of the shaft; and a conductive ring retained on the outer circumferential side of the sleeve. The device also includes a partition ring on the outer circumferential side of the sleeve having one end portion fixed to the rear bracket and the other end portion has a first flange projected in the outer diameter direction; a second flange provided on the side opposite to the rear bracket of the sleeve, having an annular wall with a concave portion, the end surface of the annular wall opposing the first flange of the partition ring; and a flat portion formed on an outer circumferential portion of the annular wall of the second flange.