To provide a device for treating muck by which the muck can be sifted surely and crushed surely even when the muck has high viscosity or high moisture content.

A roll screen 6 arranged under a receiving hopper 5 is disposed aslant so that the downstream side of the raw material moving side is higher than the upstream side. A plurality of raw material passages extending zigzag in the raw material moving direction are arranged on each of a plurality of rotating rolls of the screen 6 by disposing a plurality of rotating rollers, each of which is inclined with respect to the axial direction being the center of the radial direction of the screen 6, at the prescribed pitches to the axial direction and forming an inclined circumferential groove having the prescribed width between the adjacent rotating rollers. A crushing cutter 7 is arranged at the upper position of the screen 6 for crushing the raw material moving on the raw material passages of the screen 6.