The invention provides a sand and stone sorting device for mechanical engineering. The sand and stone sorting device comprises a coarse screening net, a positioning block, a fine screening net, sand storing chamber, a sliding plate, a driven wheel, an alternating-current motor, a conveying belt and a scraping block; the sand storing chamber is formed in the lower side in a screening box, the finescreening net is placed on the upper side of the sand storing chamber, and the coarse screening net is placed on the upper side of the fine screening net; and the positioning block is assembled on theleft side of the lower end face of the coarse screening net. Through the design, the problem that an original screening box is poor in sand and stone sorting effect is solved, the alternating-currentmotor is mounted on the lower side in a feeding box, the driven wheel is assembled on the upper side of the alternating-current motor, the conveying belt is mounted on the annular side face of the driven wheel, the sliding plate is assembled on the upper side of the driven wheel, and the scraping block is mounted on the lower side of the conveying belt; and through the design, the problem that asfor original sand and stone sorting, manual conveying is needed for sorting is solved, and the sand and stone sorting device is reasonable in structure, good in sorting effect and high in working efficiency.