PURPOSE: To perform the control corresponding to the actual grinding state of a grinder by controlling the operation state of the grinder by comparing the reference acoustic characteristic generated when the grinder is in a required operation state with the actual acoustic characteristic generated during the grinding operation of the grinder.

CONSTITUTION: An actual acoustic characteristic detection means 43 analyzes frequency distribution from the acoustic signal Sr from the microphone 46 arranged in the vicinity of the rotary cylinder of a grinder 10 to output the same as an actual acoustic characteristic Fr. A plurality of reference acoustic characteristics are stored in a reference acoustic characteristic memory means 44 at every conditions such as a grinding particle size or the like and a predetermined reference acoustic characteristic Fn is outputted corresponding to a calling request. An operation state control means 45 reads the reference acoustic characteristic Fn corresponding to the setting of the operation condition of a grinding apparatus 1 set by a control part 41 from the reference acoustic characteristic detection means 44 and the actual acoustic characteristic Fr of the grinder 10 during operation is monitored by the actual acoustic characteristic detection means 43 and the respective characteristics Fn, Fn are compared to extract the difference therebetween and the control part 41 is adjusted so that the actual acoustic characteristic Fr approaches the reference acoustic characteristic Fn.