A chair includes a base, a seat board, a frame unit, a backrest and two armrests. The base has a cylinder, legs, and casters. The seat board is connected to the top of the base and a support frame is connected to the base so as to be connected with the frame unit. The backrest and the two armrests are detachably connected to the frame unit. The backrest and the two armrests are made by durable Nylon so as to have proper curvatures that meet ergonomic requirements. The material of the backrest and the armrests can be detached and/or replaced.