An AC generator slip ring device comprising: a shaft rotatably supported by a front bracket and a rear bracket, and having a rotor arranged on the inner circumferential side of a stator; a sleeve fixed to an end portion on the rear bracket side of said shaft; and a conductive ring retained on the outer circumferential side of said sleeve, and connected to an excitation coil of said rotor, wherein said AC generator slip ring device is provided with: a partition ring which is provided on the outer circumferential side of said sleeve, and in which one end portion is fixed to said rear bracket and the other end portion has a first flange that is projected in the outer diameter direction; a second flange which is provided on the side opposite to said rear bracket of said sleeve, and has an annular wall that is formed with a concave portion so that the other end portion of said partition ring is positioned, the end surface of the annular wall being opposed to said first flange of said partition ring; and a flat portion formed on an outer circumferential portion of the annular wall of said second flange as a conveyance positioning, wherein the flat portion is provided only at a base portion of the annular wall of said second flange. a shaft rotatably supported by a front bracket and a rear bracket, and having a rotor arranged on the inner circumferential side of a stator; a sleeve fixed to an end portion on the rear bracket side of said shaft; and a conductive ring retained on the outer circumferential side of said sleeve, and connected to an excitation coil of said rotor, wherein said AC generator slip ring device is provided with: a partition ring which is provided on the outer circumferential side of said sleeve, and in which one end portion is fixed to said rear bracket and the other end portion has a first flange that is projected in the outer diameter direction; a second flange which is provided on the side opposite to said rear bracket of said sleeve, and has an annular wall that is formed with a concave portion so that the other end portion of said partition ring is positioned, the end surface of the annular wall being opposed to said first flange of said partition ring; and a flat portion formed on an outer circumferential portion of the annular wall of said second flange as a conveyance positioning, wherein the flat portion is provided only at a base portion of the annular wall of said second flange. a partition ring which is provided on the outer circumferential side of said sleeve, and in which one end portion is fixed to said rear bracket and the other end portion has a first flange that is projected in the outer diameter direction; a second flange which is provided on the side opposite to said rear bracket of said sleeve, and has an annular wall that is formed with a concave portion so that the other end portion of said partition ring is positioned, the end surface of the annular wall being opposed to said first flange of said partition ring; and a flat portion formed on an outer circumferential portion of the annular wall of said second flange as a conveyance positioning, wherein the flat portion is provided only at a base portion of the annular wall of said second flange.