Abstract: A chair has a body support structure with a membrane that can be stretched in an intended three-dimensional shape. The structure includes a frame member in a three-dimensional shape and forming a three-dimensional body support face expanding in three axes (y-axis direction), (x-axis direction), and (z-axis direction) orthogonal to each other and a membrane with peripheral edge portion fixed to the frame member under no tension or tension lower than tension required of the body support face, which has different heat shrinkage ratios in two directions, and to which the tension required of the body support face is imparted by heat shrinkage by heating after the fixing and a difference in tension generated in the heat shrinkage of the membrane forms the three-dimensional body support face.

Abstract: A chair has a body support structure with a membrane that can be stretched in an intended three-dimensional shape. The structure includes a frame member in a three-dimensional shape and forming a three-dimensional body support face expanding in three axes (y-axis direction), (x-axis direction), and (z-axis direction) orthogonal to each other and a membrane with peripheral edge portion fixed to the frame member under no tension or tension lower than tension required of the body support face, which has different heat shrinkage ratios in two directions, and to which the tension required of the body support face is imparted by heat shrinkage by heating after the fixing and a difference in tension generated in the heat shrinkage of the membrane forms the three-dimensional body support face.