The present claimed invention intends to provide a chair having a frame structure that is effective for securing a required strength without needless structure to reinforce the strength.The chair has a chair body A comprising a seat frame 12, a back frame 22 and a rib that reinforces between the seat frame 12 and the back frame 22, wherein the rib is formed to extend to a side direction so as to be used as an arm frame 71, and the seat frame 12, the back frame 22 and the arm frame 71 are continuously and integrally formed three-dimensionally, and openings 12a, 22a into which a mesh member 13, 23 to form a seating face is fitted are arranged at the seat frame 12 and the back frame 22 respectively.