PURPOSE: To provide a controller for electric motor Mich can attain fast response speed and stable control over the whole range of rotational speed at the time of controlling the rotating position and rotational speed of an electric motor.

CONSTITUTION: This controller 20 is provided with the first addition operating device 21, a position gain operating device 21, the first gain regulating device 23, the second addition operating device 24, a speed gain operating device 25, a torque control means 9, a speed operating device 3, and a position operating device 4. By the detecting signals of a pulse encoder 2 mechanically-connected with an electric motor 1, the rotating position and the rotational speed of the electric motor 1 are controlled, and the first gain regulating device 23 decreases the gain of the position gain operating device 21 and the speed gain operating device 25 in the low rotational speed range of the electric motor 1, and increases gain in the medium and high rotational speed ranges.