To provide a chair which has an excellent cost performance and a wide range of application scale, and which is easy to recycle from the aspect of the environment.

A seating surface C made of recycled plastic, where bottle caps are taken into the structure in advance, is produced. By screwing in and joining an empty PET bottle A, it can be used as a chair easily. A number of variations can be achieved such as a square shape, a triangular shape, a fan shape, a circular shape and so on. Further, by joining seating surfaces, S-shape, ?-shape and a bench shape can be assembled easily.