An axial gap rotating electrical machine comprising: a rotating shaft having a stepped portion between a large diameter portion and a small diameter portion; a rotor comprised of an annular rotor yoke secured on the small diameter portion of the rotating shaft in tight contact with the stepped portion and a permanent magnet secured on the inside surface of the rotor yoke; a first housing holding a first bearing rotatably supporting the rotating shaft; a stator positioned and secured by a stepped portion formed in the inner circumferential wall of the first housing so that the stator is opposed to the permanent magnet with a predetermined air gap (g) in-between on the inner circumference of the first housing; and a second housing coupled with the first housing and having therein a second bearing which rotatably supports the rotating shaft; the permanent magnet is a ring magnet that is comprised of multiple magnetic pole pieces; the inner circumferential portion of the rotor yoke and the outer circumferential portion of the small diameter portion of the rotating shaft are secured together by knurling; the first bearing is positioned by a securing portion (22A-2) which is provided in the rotor yoke and secures the rotor yoke on the small diameter portion of the rotating shaft, wherein the securing portion (22A-2) provided in the rotor yoke is a one-sided boss portion (22A-2) or a double-sided boss portion (22A-2); the boss portion (22A-2) of the rotor yoke is sandwiched and secured between the first bearing and the stepped portion of the rotating shaft; the boss portion (22A-2) provided in the rotor yoke positions an inner ring of the first bearing, and an outer ring of the first bearing is secured in the first housing; the rotor yoke has an outer circumferential wall portion erected in the axial direction and an inner circumferential wall portion erected in the axial direction, the ring magnet is placed in an annular groove portion therebetween, a dam portion having a V-shaped cross section is circumferentially formed by swaging in the inner circumferential wall portion in proximity to an inner circumferential portion of the ring magnet of the rotor yoke, so that part of the inner circumferential wall portion is brought to an inner circumference side of the ring magnet to secure the rotor yoke and the ring magnet, and the depth of the annular groove portion is equal to 1/3 of the thickness of the ring magnet. a rotating shaft having a stepped portion between a large diameter portion and a small diameter portion; a rotor comprised of an annular rotor yoke secured on the small diameter portion of the rotating shaft in tight contact with the stepped portion and a permanent magnet secured on the inside surface of the rotor yoke; a first housing holding a first bearing rotatably supporting the rotating shaft; a stator positioned and secured by a stepped portion formed in the inner circumferential wall of the first housing so that the stator is opposed to the permanent magnet with a predetermined air gap (g) in-between on the inner circumference of the first housing; and a second housing coupled with the first housing and having therein a second bearing which rotatably supports the rotating shaft; the permanent magnet is a ring magnet that is comprised of multiple magnetic pole pieces; the inner circumferential portion of the rotor yoke and the outer circumferential portion of the small diameter portion of the rotating shaft are secured together by knurling; the first bearing is positioned by a securing portion (22A-2) which is provided in the rotor yoke and secures the rotor yoke on the small diameter portion of the rotating shaft, wherein the securing portion (22A-2) provided in the rotor yoke is a one-sided boss portion (22A-2) or a double-sided boss portion (22A-2); the boss portion (22A-2) of the rotor yoke is sandwiched and secured between the first bearing and the stepped portion of the rotating shaft; the boss portion (22A-2) provided in the rotor yoke positions an inner ring of the first bearing, and an outer ring of the first bearing is secured in the first housing; the rotor yoke has an outer circumferential wall portion erected in the axial direction and an inner circumferential wall portion erected in the axial direction, the ring magnet is placed in an annular groove portion therebetween, a dam portion having a V-shaped cross section is circumferentially formed by swaging in the inner circumferential wall portion in proximity to an inner circumferential portion of the ring magnet of the rotor yoke, so that part of the inner circumferential wall portion is brought to an inner circumference side of the ring magnet to secure the rotor yoke and the ring magnet, and the depth of the annular groove portion is equal to 1/3 of the thickness of the ring magnet.