To pile up a number of chairs in a low height by projecting out the back part of a seat panel and forming a plurality of recessed parts or projecting parts and projecting parts or recessed parts corresponding thereto on the projected part and making a flat condition where the seat panel is stored in a front leg and the front leg is stored in the back leg when the chair is folded.

When a chair is folded, by taking up a back leg 8 and extending it through a rod or rotating the front end side of a seat panel 3 in the clockwise direction around a shaft 1a as a center and rotating thereby the lower end side of the base part 81 to the lower end side of the front leg 1, the seat panel 3 is rotated in the clockwise direction around the shaft 1a of the fixed part to the front leg 1 and when the front leg 1 is made to be fallen down to the left, the seat panel 3 is made to be stood and is stored in the front leg 1 and the front leg 1 is stored in the back leg 8 and as the result, the chair is folded into a flat condition. In this state, when chairs are successively piled up, the projecting parts 6 of the seat panel 3 of the upper chair are fitted in the recessed parts of the seat panel 3 of the lower chair and the back rests 2 are also piled up and after they are piled up, even if an external force is applied, there exists no possibility of collapsing the piled-up condition.