A motor speed control device for a rolling mill, which includes a rolling roll that rolls a metal material, a roll rotation shaft directly connected to the rolling roll, a motor rotation shaft that transmits power to the roll rotation shaft, and a motor that drives the motor rotation shaft, includes: a non-contact type speed sensor arranged at a position close to the rolling roll with spacing to a circumferential surface of the roll rotation shaft to detect a roll rotation shaft angular speed of the roll rotation shaft; and a speed controller that controls a speed of the motor based on a comparison value between an actual value and a target angular speed of the rolling roll so that the actual value coincides with the target angular speed. The actual value is the roll rotation shaft angular speed to be fed back to the speed controller.