The related control device of electric motor that dentist's dental drill of driving cutting element is rotated with motor of system of the present invention, characteristic are as follows: the control device of electric motor is to have load torque test section, to detect the load torque of cutting element receiving； And rotation speed test section, to detect the rotation speed of motor； And control unit, to control the rotation speed and motor current of motor. The control unit system load torque detected when load torque test section, when more than the torque limit value preset, restrictions motor electric current is the 1st limitation electric current. Control unit system detects that load torque is more than torque limit when rotation speed test section, and when motor has stopped rotating, and control motor current is in the 2nd limitation electric current hereinafter, the aforementioned 1st limitation electric current of the low what of the 2nd limitation electric current system.本發明係有關具有電動機以旋轉驅動切削工具之牙醫用牙鑽之電動機控制裝置，其特徵為：該電動機控制裝置，係具備負載轉矩檢測部，以檢測切削工具承受之負載轉矩；及旋轉速度檢測部，以檢測電動機之旋轉速度；及控制部，以控制電動機之旋轉速度及電動機電流。控制部係當負載轉矩檢測部所檢測出之負載轉矩，超過預先設定之轉矩限制值時，限制電動機電流為第1限制電流。控制部係當旋轉速度檢測部檢測出負載轉矩超過轉矩限制，且電動機已停止旋轉時，控制電動機電流在第2限制電流以下，該第2限制電流係低於前述第1限制電流。
