To solve the subject in a conventional foldable seat that there is no seat which is built by a face material, needs no special joint, is safe, can be employed in a free form while continuously deforming it, and is foldable.

A folding chair is given which has a mechanism which rotates a plane by using as a pivot, i.e., a bend line a pattern made by a parallel straight line group arranged on a two-dimensional plane and a polygonal line which symmetrically bends about it, that is, a structure which supports load by a table flap structure by deformation and folding performed by a mechanisms like a folded paper of bellow folding and a part touching the ground and a sitting surface part built by a ridgeline stood in a line on space, respectively. Since the mechanism is built by bending of a plane and an enough thin material can be used, a special movable joint is not needed and since the mechanism can be built by bending the face material, construction is simple and it is possible to use by safely deforming it at the time of employment.