The seat surface body 3 is constituted to be swung between a seated seate and a forward inclined state when the seated person stands up centring around the shaking fulcrum 31 provided at the front part of the seat surface body 3. 座面体3の前部に設けた揺動支点31を中心に、着座時状態と、着座者が起立時に前傾となる前傾状態とに座面体3を揺動可能に構成する。 - 特許庁