A motor-driving voltage control device that generates a driving voltage signal to be provided to a motor based on a driving command signal, characterised by: a low gradation unit that causes a gradation level of the driving voltage signal to be lowered to such a level that it falls within a resolution range of a PWM modulator and wherein the low gradation unit performs noise-shaping modulation in which quantization noise is biased toward a high-frequency range, and a said PWM modulator that modulates amplitude of the driving voltage signal to pulse width thereof, the driving voltage signal having a low gradation level generated in the low gradation unit, wherein the low gradation unit causes frequency components of quantization noise to be unevenly distributed in a frequency side having higher frequencies than a cutoff frequency of a low-pass filter that includes inductance of the motor by the noise-shaping modulation, wherein the PWM modulator supplies to the motor a driving voltage signal, the low gradation unit causing the gradation level of the driving voltage signal to be lowered and causing the frequency components of quantization noise thereof to be unevenly distributed in a frequency side having higher frequencies than the cutoff frequency of the low-pass filter that includes inductance of the motor by the noise-shaping modulation; wherein the motor-driving voltage control device further comprises a high frequency converter that increases a frequency of the driving command signal in a preceding stage of the low gradation unit, wherein the high frequency converter increases the frequency of the driving command signal above a threshold frequency to allow smoothing by the low-pass filter. a low gradation unit that causes a gradation level of the driving voltage signal to be lowered to such a level that it falls within a resolution range of a PWM modulator and wherein the low gradation unit performs noise-shaping modulation in which quantization noise is biased toward a high-frequency range, and a said PWM modulator that modulates amplitude of the driving voltage signal to pulse width thereof, the driving voltage signal having a low gradation level generated in the low gradation unit, wherein the low gradation unit causes frequency components of quantization noise to be unevenly distributed in a frequency side having higher frequencies than a cutoff frequency of a low-pass filter that includes inductance of the motor by the noise-shaping modulation, wherein the PWM modulator supplies to the motor a driving voltage signal, the low gradation unit causing the gradation level of the driving voltage signal to be lowered and causing the frequency components of quantization noise thereof to be unevenly distributed in a frequency side having higher frequencies than the cutoff frequency of the low-pass filter that includes inductance of the motor by the noise-shaping modulation; wherein the motor-driving voltage control device further comprises a high frequency converter that increases a frequency of the driving command signal in a preceding stage of the low gradation unit, wherein the high frequency converter increases the frequency of the driving command signal above a threshold frequency to allow smoothing by the low-pass filter.