Fatigue reducing seat

Provided is a seat which offers increased ride comfort and less fatigue felt even on long-time sitting. The seat includes a cushion frame, a first support member supported by the cushion frame and configured to support a seated occupant, second support members disposed at left and right sides of the first support member and configured to be deformable, and a restraining portion by which each second support member is restrained in such a manner that its laterally outer side is less likely to sink down than its laterally center side. The seat is configured such that an upper-side support surface for supporting a seated occupant is so restrained by the restraining portion as to assume a first position when no occupant is seated, and to assume a second position when an occupant is seated, the support surface facing further inward in the second position than in the first position.