To contract the area of a large-sized plate-shaped member by folding.

A folding plate-shaped member P is equipped with an integrally molded plastic main body wherein one plate-shaped member 1 and other plate- shaped member 2 both of which have a hollow double wall structure are connected in a folding state through a hinge part 4 and a skin material 3 is laminated to the surface of the main body. The hinge part 4 is equipped with one connection part 6a of such a state that the surface wall 1a of one plate-shaped member 1 projects from an end wall 1c, other connection part 6b of such a state that the surface wall 2a of the other plate-shaped member 2 projects from an end wall 2c, the almost V-shaped bent part 5 connected to one connection part 6a and the other V-shaped bent part 7 connected to the other connection part 6b and one almost V-shaped bent part 5 and the other almost V-shaped bent part 7 are parallelly arranged and a flat part 6c is interposed between both of them.