Worm reduction gear

摘要

A worm reduction gear (2) that reduces a rotation of a worm (10) and transmits the reduced rotation to a worm wheel (20) includes a casing that houses the worm and the worm wheel, wherein the casing includes: a wheel opposing surface (51a) that opposes an end surface (20b) of the worm wheel via an interval (53); and a grease holding recessed portion (52) formed in a recessed shape in the wheel opposing surface, wherein the grease holding recessed portion is provided in a position opposing a worm meshing portion (60) between the worm and the worm wheel.