A chair with a foldable desk includes a support leg having a crossbar. A seat plate installed above said support leg includes an upper seat, a lower cover and a coupler into which the crossbar is rotatably inserted. The seat plate rotates between a vertical position and a horizontal position. A back installed above a rear side of the seat plate is capable of tilting forward and rearward with tilting means. A desk installed above a side of the support leg includes an upper plate with an attachment member on its bottom. The upper plate may swing between an upper position and a lower position within an angle range.