Abstract: A sun shield device for automobile includes a tubular central axle, a revolving sleeve which has a diameter larger than and a length shorter than that of the central axle being rotatably supported around the central axle, a shading sheet engaged on and wound around the revolving sleeve, an auto-rewinding device which is installed between the central axle and the revolving sleeve for driving the revolving sleeve to rotate so as to automatically rewind the shading sheet around the revolving sleeve, a supporting device including a pair of supporters extendably connected to two ends of the central axle respectively, and an adjusting device for adjusting the length of at least one of the supporters so as to adjust an overall length of the sun shield device until two supporting end members of the two supporters respectively firmly pressed against two interior side walls of a trunk of an automobile so as to horizontally support the sun shield device within the trunk.