To provide a chair with a flip-up seat which has a comfortable feeling of sitting while suppressing manufacturing cost.

The chair includes a chair body having a support rod 4 having the axis directed to a right and left direction, and a resin seat plate 1 vertically turnable around the support rod 4 of the chair body. The chair body is provided with support frames 3 each having a back end part arranged on the lower surface side of the seat plate 1 vertically and turnably engaged with the support shaft 4, and the front part and the rear part of the plate 1 are supported by the support frames 3 so that an intermediate part 112 of the seat plate 1 is bent in a thickness direction when using the seat plate 1 substantially horizontally.