A seat cushion of vehicle seat including a seat cushion frame and a bottom panel member on which a foam padding is mounted. The bottom panel member has a thigh support area fixed to a forward portion of the seat cushion frame and a buttocks support area situated in a rearward portion of the seat cushion frame. The buttocks support area has a resiliently deformable area in which are formed beads, each being resiliently stretchable laterally relative to the central line thereof by a downward load applied to the buttocks support area, whereby the resiliently deformable area is rendered deformable and displaceable downwardly. The buttocks support area may be made narrow by forming two inwardly curved edge portions in the respective sides thereof to thereby allow that buttocks support area to be warped downwardly. Hence, the buttocks support area is resiliently displaceable vertically relative to the seat cushion frame.