To enhance the working efficiency by rotating a rotor fitted at the periphery with a striking plate by a hydraulic motor, installing reflection plates as mating with the striking plate, and mounting a bracket removably on an arm of a hydraulic excavating machine having a travelling device.

When oil pressure is supplied to a hydraulic motor to rotate a rotor 20, the material to be crushed which is supplied from the inlet 16h of a casing 16 to the gap between a striking plate 21 and the first reflection plate 31 is crushed into earth and sand and is exhausted downward while it is further crushed into finer particles in the gap between the striking plate 21 and the second reflection plate 32. When the gap between the striking plate 21 and any reflection plate 31, 32 is clogged with the material, a shaft 30 is removed, and the rear wall 16g is taken out from the casing 16 together with the reflection plates 31, 32, and now it is possible to remove the clogging material. A bracket 38 is mounted on a rotary shaft at the tip of the arm, and thereby a bucket 40 and a rotary crusher 11 can be rotated in the direction up and down.