To provide a controller for suppressing speed variation caused in changing a gain, and for preventing orbit precision for a command value from being deteriorated even when a gain is changed in real time.

This controller is provided with a command generation part 2 for generating a position command; a gain control part 3 for changing a gain in predetermined timing, and for outputting it to a servo control part 2; a position command correcting part 4 for correcting a position command to be output by the command generation part 2, and for generating a correction position command; and a servo control part 1 for driving a motor on the basis of the correction position command and the changed gain from the gain control part 3.