A worm wheel comprising: a metal hub (11b, 11d), and a gear portion; the hub (11b, 11d) comprising: an installation hole that is provided in a center portion of the hub (11b, 11d) for fitting and fastening inside a rotating shaft; a first annular concave portion that is provided on an inner diameter side of the hub (11b, 11d) on one surface in an axial direction of the hub (11b, 11d), the first annular concave portion being recessed in the axial direction; concave and convex portions in a circumferential direction of the hub (11b, 11d) that are provided around an outer circumferential edge portion of the hub (11b, 11d): the gear portion being formed by a synthetic resin that covers an entire circumference of an outer diameter side end portion of the hub (11b, 11d); characterized in that a second annular concave portion is provided in a portion on an outer diameter side of the hub (11b, 11d), the second annular concave portion is formed so as to be further concave from an inner surface at a portion on the outer diameter side of the first annular concave portion, and the second annular concave portion is formed so as to be concave outward in the radial direction from a circumferential surface on the outer-diameter side of the inner surface of the first annular concave portion, the second annular concave portion is formed as an annular concave groove having a V-shaped cross section with a width dimension thereof becoming smaller toward a rear portion thereof, and an inner circumferential edge portion of the gear portion that is located on the one surface side in the axial direction of the hub (11b, 11d) fits inside a portion near the outer diameter of the first annular concave portion, and part of the synthetic resin forming the gear portion also fills the second annular concave portion. a metal hub (11b, 11d), and a gear portion; the hub (11b, 11d) comprising: an installation hole that is provided in a center portion of the hub (11b, 11d) for fitting and fastening inside a rotating shaft; a first annular concave portion that is provided on an inner diameter side of the hub (11b, 11d) on one surface in an axial direction of the hub (11b, 11d), the first annular concave portion being recessed in the axial direction; concave and convex portions in a circumferential direction of the hub (11b, 11d) that are provided around an outer circumferential edge portion of the hub (11b, 11d): the gear portion being formed by a synthetic resin that covers an entire circumference of an outer diameter side end portion of the hub (11b, 11d); characterized in that a second annular concave portion is provided in a portion on an outer diameter side of the hub (11b, 11d), the second annular concave portion is formed so as to be further concave from an inner surface at a portion on the outer diameter side of the first annular concave portion, and the second annular concave portion is formed so as to be concave outward in the radial direction from a circumferential surface on the outer-diameter side of the inner surface of the first annular concave portion, the second annular concave portion is formed as an annular concave groove having a V-shaped cross section with a width dimension thereof becoming smaller toward a rear portion thereof, and an inner circumferential edge portion of the gear portion that is located on the one surface side in the axial direction of the hub (11b, 11d) fits inside a portion near the outer diameter of the first annular concave portion, and part of the synthetic resin forming the gear portion also fills the second annular concave portion. an installation hole that is provided in a center portion of the hub (11b, 11d) for fitting and fastening inside a rotating shaft; a first annular concave portion that is provided on an inner diameter side of the hub (11b, 11d) on one surface in an axial direction of the hub (11b, 11d), the first annular concave portion being recessed in the axial direction; concave and convex portions in a circumferential direction of the hub (11b, 11d) that are provided around an outer circumferential edge portion of the hub (11b, 11d): the gear portion being formed by a synthetic resin that covers an entire circumference of an outer diameter side end portion of the hub (11b, 11d); characterized in that a second annular concave portion is provided in a portion on an outer diameter side of the hub (11b, 11d), the second annular concave portion is formed so as to be further concave from an inner surface at a portion on the outer diameter side of the first annular concave portion, and the second annular concave portion is formed so as to be concave outward in the radial direction from a circumferential surface on the outer-diameter side of the inner surface of the first annular concave portion, the second annular concave portion is formed as an annular concave groove having a V-shaped cross section with a width dimension thereof becoming smaller toward a rear portion thereof, and an inner circumferential edge portion of the gear portion that is located on the one surface side in the axial direction of the hub (11b, 11d) fits inside a portion near the outer diameter of the first annular concave portion, and part of the synthetic resin forming the gear portion also fills the second annular concave portion.