A chair has a chair back including a frame, two supporting legs and a bearing plate. The frame is integrated to the supporting legs in an injection molding manner. The bearing plate is integrated to a bottom frame portion and two side frame portions of the frame in the injection molding manner so that a user can lean against the bearing plate. The two side frame portions are located on two opposite sides of the bottom frame portion. The hardness of the bearing plate is lower than the hardness of the frame, and the hardness of the frame is lower than the hardness of the supporting leg. Therefore, two members whose materials are different in hardness are possibly constitute a chair back formed in one piece.