The invention discloses a backrest seat with a telescopic sunshade. The backrest seat comprises a chair back, a seat surface and chair legs, wherein a containing cavity is formed in the chair back; the telescopic sunshade is arranged in the containing cavity and is composed of two sunshade frames and sun cloth; the two sunshade frames are respectively hinged to the tops of two brackets through two first pin shafts; the sunshade frames can rotate around the first pin shafts; the sun cloth is supported between the two sunshade frames; the section of the sunshade frames is in the shape of a right-side inverted U and is formed by encircling of two side arms and a bottom arm; first ends of two supporting rods are respectively hinged to the upper ends of the two brackets through second pin shafts; clamping hooks are arranged at second ends of the supporting rods; a clamping shaft is arranged at the middle position of the sunshade frames; two ends of the clamping shaft are respectively fixed on the two side arms of the sunshade frames; and the clamping hooks can be clamped with the clamping shaft. When sun shading or rain shading is needed, the sunshade is pulled out and unfolded, and the sunshade is folded into the containing cavity when sun shading or rain shading is not needed, so that the human needs are met, long-term exposure to the sun and rain can be avoided, and the service life of the sunshade is prolonged.