To provide a folding chair whose rectangular seat surface part can be used.

The folding chair includes two front side leg pats 100a, two rear side leg parts 100b, four X-shaped legs 200 disposed between the two front side leg parts and rear side leg parts 100a and 100b, and a seat surface part 300 attached to the front side leg parts and rear side leg parts 100a and 100b. The front side leg parts 100a has cylindrical front side movable parts 100a externally ring-fitted so as to be freely vertically moved, and the rear side leg parts 100b are provided with cylindrical rear side movable parts 110b externally ring-fitted so as to be freely vertically moved. While the first and second legs 210a and 210b of the front side and rear side X-shaped legs 200 are freely turnably attached to the upper end parts of the front side movable parts 110a and the rear side movable parts 110b at one end, the first and second legs 210a and 210b of the X-shaped legs 200 on both side face sides are freely turnably attached to the lower end parts of the front side movable parts 110a and the rear side movable parts 110b at one end.