Abstract: A chair includes a chair leg, a backrest, a seat and a support member. The chair leg includes a stem that has a connecting end at a top thereof. The seat is integrally formed and has a seat frame, two reinforcement beams and a support member disposed between the reinforcement beams. The support member includes a plurality of ribs, and an axle connecting portion and an adjusting portion surrounded by the ribs. The axle connecting portion has an axle hole to couple with the connecting end. The support member has a support portion below the axle connecting portion. The adjusting portion includes a fixation hole. A bottom of the support member includes an axle mounting flange. One end of a support beam connects with the backrest and the other end of the support beam pivotally connects with the axle mounting flange.