To adjust a crushing gap without obstacle by measuring the oscillation of an impact mechanism and recording a zero position if the measured value is over an oscillation limit value in a crushing machine of such type that the impact mechanism is back turned by a distance corresponding to the desired crushing gap.

The crushing machine has an impact mechanism 13 and an impact tool 11. A gap therebetween is adjustable, the impact mechanism 13 is turned to the position for the impact mechanism to come into contact with the impact tool 11 during a rotor 12 rotates, the position of the impact mechanism 13 in relation to this state is detected as a zero position and, subsequently, the impact mechanism 13 is turned to the position to attain a desired crushing gap. In the crushing machine of this type, an oscillation of the impact mechanism 13 is measured and if the measured value exceeds a predetermined oscillation limit value, a zero position is recorded, and at the same time, in this case, a back turning movement of the impact mechanism 13 by a distance corresponding to the desired cap is generated.