A motor controller which controls a servo motor for driving a machine, includes: a speed command unit which commands the speed of the machine; a speed detection unit which detects the speed of the servo motor; and a speed control unit which produces a torque command based on a speed command and a motor speed detected so as to control the speed of the servo motor, where the speed control unit includes a filter which approximates the inverse characteristic of a transmission characteristic from the servo motor to the machine, the filter has a transmission characteristic F(s) based on a frequency , a vibration damping coefficient and a cutoff frequency .sub.adj which are adjustment parameters and the frequency is adjusted so as to be equal to or more than an antiresonant frequency .sub.0 of the machine but less than a resonant frequency .sub.p.

A motor controller which controls a servo motor for driving a machine, includes: a speed command unit which commands the speed of the machine; a speed detection unit which detects the speed of the servo motor; and a speed control unit which produces a torque command based on a speed command and a motor speed detected so as to control the speed of the servo motor, where the speed control unit includes a filter which approximates the inverse characteristic of a transmission characteristic from the servo motor to the machine, the filter has a transmission characteristic F(s) based on a frequency , a vibration damping coefficient and a cutoff frequency .sub.adj which are adjustment parameters and the frequency is adjusted so as to be equal to or more than an antiresonant frequency .sub.0 of the machine but less than a resonant frequency .sub.p.