Abstract: The present invention realizes spreading a sheet on a frame member by a simple structure and a simple process, and prevents uneven tension charged against the sheet. In the sheet spreading method of the invention, a core member for a backrest of a chair which is heated to around 200.degree. C. in a furnace is put into a flow dipping tank filled with powder resin. As a result, a resin coating is formed on the surface of the pipe constituting the core member. Also, a mesh is placed on a metal mold and clamped. Since a recess corresponding to the shape of the core member is formed in the top side of the metal mold, the mesh is spread on the core member with a tension charged against when the core member having the above-mentioned coating is pressed into the recess.