To suppress bite-in and clogging yielded when a supplied material to be crushed is crushed by the free hammer-like crushing blade body provided on the peripheral surface of the crushing barrel revolved in a crushing chamber to reduce the interruption of work for eliminating clogging to perform crushing work.

A rake-in wheel 4, which is conducted to the output shaft (e) of a motor E through a conduction mechanism (D) and rotationally driven so as to scrape up the material W to be crushed to send the same to the crushing chamber 1, is supported on the leading end side of the support arm 40 revolved centering around a rotary main shaft 20 to rise and fall, and a transmission mechanism G is incorporated in the conduction mechanism D for conducting the rake-in wheel 4 and the output shaft (e) of the motor E. Then, the transmission mechanism G is allowed to cooperate with a support arm 40 so that variable speed operation is performed by the rising and falling operation of the support arm 40 to perform control not only to lower the rotational speed of the rake-in wheel 4 by the rising revolution of the support arm 40 but also to increase the rotational speed of the rake-in wheel 4 by the falling revolution of the support arm 40.