To prevent clogging of a sieve, to enable the selection of construction by-products which has been impossible to be performed, and to select efficiently by improving the treatment capacity by installing a swinging mount and a vibration motor in the lower part of a hopper, and an agitator is arranged on the bottom surface of the hopper.

At least two wide spaces 16, 17 are formed in a frame body with partition frames 19a, 19b, a net conveyer 6 and a sieve frame 15 are arranged in the spaces 16, 17, and the mesh size is decreased in turn from the conveyer 6 toward the sieve frame. When construction by-products are charged from a hopper 1 installed in the uppermost stage, a swinging mount 3 is actuated by a vibration motor 13 to lead the by-products to the bottom surface, a clogging in the lower part of the hopper 1 is prevented, and simultaneously a proper amount of them are discharged to the next conveyer 6 through a guide plate 4.