To solve the problem that the size of a seat of a conventional chair is too small to sit with the legs crossed or tucked under the body because the seat is designed to sit with the legs hung down and if the seat size is designed for sitting with the legs crossed or tucked under the body, it is impossible or difficult to sit normally with the legs hung down.

This chair is constituted so that parts in front of and on both sides of the seat, where the seat is relatively widened, are movable with a reclining system or slidable under the seat. With this constitution, the seat size is controllable and, therefore, adjustable for various ways of sitting.