Seat adjusting apparatus for vehicle

A seat adjusting apparatus (20) for a vehicle includes a supporting member (8) pivotally supported at a base member (21) by means of a first bearing (23), a pinion gear (25) driven by a driving device (12), a sector gear (24) engageable with the pinion gear and a restriction mechanism (27, 37) formed at the sector gear for restricting a relative rotation between the pinion gear and the sector gear. The restriction mechanism includes a contact portion (27, 37) coming in contact with the pinion gear so that a component force of a reaction force (F2, F4), which works in a direction in which the first bearing is separated from the second bearing (28), acting on the pinion gear is reduced. A thickness (T) of a first tooth root (24d) of a tooth (24c) included in the teeth formed at the sector gear is larger than a thickness (t) of a second tooth root of the other teeth formed at the sector gear.