The utility model discloses a flat processing device for rejected plates, which comprises a plurality of ladder-shaped iron blocks, a hoisting steel wire rope and a safe steel wire rope. A plurality of connecting ear rings are arranged on two sides at the lower part of each ladder-shaped iron block; a safe ear ring is arranged at the top part of each ladder-shaped iron block; the ladder-shaped iron blocks are connected in sequence; the connecting ear rings of the two adjacent ladder-shaped iron blocks correspond to each other and are connected through a pin shaft; two ends of the hoisting steel wire rope are respectively connected with the connecting ear rings of the two ladder-shaped iron blocks positioned on the outermost side; and the safe steel wire rope penetrates through the safe ear rings at the top parts of the ladder-shaped iron block in sequence. The flat processing device for the rejected plates improves the utilization value of the rejected plates and simultaneously improves the production efficiency.