A worm wheel includes: a sleeve; and a toothed portion provided by injection molding so as to cover a part of the sleeve, the toothed portion including a first thick portion provided on a first side face, which is a surface of the sleeve on a side closer to an injection-mold gate in an axial direction, and a second thick portion provided on a second side face, which is a surface on an opposite side to the first side face. A central part, in the axial direction, of the outer peripheral surface of the sleeve projects in the radial direction relative to both ends in the axial direction. The first thick portion of the toothed portion has a smaller thickness in the axial direction than the second thick portion.

The present embodiments relate to a worm wheel of a steering system speed reducer, and provide a worm wheel of a steering system speed reducer, and a manufacturing method therefor, the worm wheel comprising: an external toothed part having a ring shape, external gear teeth provided on the outer peripheral side thereof, insertion grooves provided on the inner peripheral side thereof, and coupling holes provided on the upper surface and/or the lower surface thereof; an internal toothed part, which has a ring shape, is inserted into the external toothed part, has insertion protrusions provided on the outer peripheral side thereof, and has coupling protrusions provided at locations corresponding to the coupling holes; a hub to which a steering shaft is coupled; and a boss part provided between the outer peripheral side of the hub and the inner peripheral side of the external toothed part.

A worm wheel includes: a sleeve; and a toothed portion provided by injection molding so as to cover a part of the sleeve, the toothed portion including a first thick portion provided on a first side face, which is a surface of the sleeve on a side closer to an injection-mold gate in an axial direction, and a second thick portion provided on a second side face, which is a surface on an opposite side to the first side face. A central part, in the axial direction, of the outer peripheral surface of the sleeve projects in the radial direction relative to both ends in the axial direction. The first thick portion of the toothed portion has a smaller thickness in the axial direction than the second thick portion.