PURPOSE: To discriminate waste of specific sizes from waste having various kinds of sizes.

CONSTITUTION: This sieving device has conveyors 3 disposed horizontally within a casing 1, plural sheets of scrapers 4 fixed to these conveyors 3, a bag rupturing machine 5 disposed above the feed side conveyor 3A, waste splashing preventive means 8 disposed in proximity to this bag rupturing machine 5 and plural pieces of sieving bars 9 fixed between the upstream side of the feed side conveyor 3A and the lower part of the bag rupturing machine 5. The device consists of a blind plate 10 fixed to the lower side of the feed side conveyor 3A not fixed with these bars 9, a discharge chute 11 for large-sized waste disposed on the downstream side of the feed side conveyor 3A, a discharge chute 12 for small-sized waste disposed at the downstream end of the return side conveyor 3B, a bottom plate 13 disposed at the downstream end of the return side conveyor 3B and a driving means 14 for driving the conveyors 3 and the bag rupturing machine 5.