A worm wheel (10, 10A, 10B, 10C, 10D) comprising: a disk-shaped core (1, 1A, 1B, 1C, 1D) made of metal; and an annular rim portion (2, 2A, 2B, 2C, 2D) made of synthetic resin and covering an outer circumferential portion of the core; wherein a gear is formed on an outer circumferential portion of the rim portion, wherein the rim portion is integrally formed with the core (1, 1A, 1B, 1C, 1D) by synthetic resin injection molding, wherein the core (1, 1A, 1B, 1C, 1D) comprises a center hole into which a shaft is capable of being fitted, an axial end surface formed with a first annular recess, the core further comprises another axial end surface formed with a second annular recess (13, 13A, 13B), characterized in that the rim portion comprises a first inner circumferential portion extending from an axial end surface of the rim portion to the radially outer region of the first annular recess and fixed to the radially outer region of the first annular recess, and a second inner circumferential portion (23, 23A, 23B) extending from another axial end surface of the rim portion to a radially outer region of the second annular recess (13, 13A, 13B) and fixed to the radially outer region of the second annular recess (13, 13A, 13B), an outer circumferential wall surface (13c, 13Ac, 13Bc) of the second annular recess (13, 13A, 13B) extends from a bottom surface (13d, 13Ad, 13Bd) of the second annular recess (13, 13A, 13B) so as to be perpendicular to the bottom surface (13d, 13Ad, 13Bd), and a depth of the second annular recess (13, 13A, 13B) is at least 0.1 mm but not deeper than half of an axial distance between the other axial end surface of the core and the other axial end surface of the rim portion. a disk-shaped core (1, 1A, 1B, 1C, 1D) made of metal; and an annular rim portion (2, 2A, 2B, 2C, 2D) made of synthetic resin and covering an outer circumferential portion of the core; wherein a gear is formed on an outer circumferential portion of the rim portion, wherein the rim portion is integrally formed with the core (1, 1A, 1B, 1C, 1D) by synthetic resin injection molding, wherein the core (1, 1A, 1B, 1C, 1D) comprises a center hole into which a shaft is capable of being fitted, an axial end surface formed with a first annular recess, the core further comprises another axial end surface formed with a second annular recess (13, 13A, 13B), characterized in that the rim portion comprises a first inner circumferential portion extending from an axial end surface of the rim portion to the radially outer region of the first annular recess and fixed to the radially outer region of the first annular recess, and a second inner circumferential portion (23, 23A, 23B) extending from another axial end surface of the rim portion to a radially outer region of the second annular recess (13, 13A, 13B) and fixed to the radially outer region of the second annular recess (13, 13A, 13B), an outer circumferential wall surface (13c, 13Ac, 13Bc) of the second annular recess (13, 13A, 13B) extends from a bottom surface (13d, 13Ad, 13Bd) of the second annular recess (13, 13A, 13B) so as to be perpendicular to the bottom surface (13d, 13Ad, 13Bd), and a depth of the second annular recess (13, 13A, 13B) is at least 0.1 mm but not deeper than half of an axial distance between the other axial end surface of the core and the other axial end surface of the rim portion.