To provide a crusher which ensures compatibility between cleaning for removing wood chips stuck to a screen in a wind generated by a crushing rotor and reduction of noise in crushing wood or damage to the crushing rotor.

A crushing rotor motor 70 has a variable displacement mechanism 71, and a control piston 72 and a capacity control valve 76 in the variable displacement mechanism 71 are interlocked. A switching valve 81 can be selectively switched between an initial position 81d which communicates pipe paths 85, 87 with each other and prevents the capacity control valve 76 from actuating pilot pressure, and an operating position 81e which communicates pilot paths 86, 87 with each other and allows the capacity control valve 76 to actuate the pilot pressure. The capacity control valve 76 in such a state that the pilot pressure is actuated regulates the movement of the variable displacement mechanism 71 of the direction for increasing a capacity of the crushing rotor 13. The upper limit of the rotational speed of the crushing rotor 13 is set to a first upper limit suitable for crushing at the initial position 81d of the switching valve 81 and is set to the second upper limit (>the first upper limit) suitable for cleaning at the operating position 81e.