A motor eccentricity measuring apparatus is provided comprising a detecting device for detecting a deflection of the rotating shaft of a motor, a first, a second, and a third hold device for holding detected values supplied from the detecting device, and an amplifier device for amplifying a difference between two outputs of the first and the second hold device. In operation, RRO is calculated, during a first measuring period, from the detected values of the first and third hold device and NRRO is calculated, during a second measuring period, from the detected values of the first and second hold device and simultaneously, amplified with the amplifier device.