A motor driving device, which controls a rotation number of a brushed motor by outputting a command signal to a motor controller placed in a current supply path, includes: a noise detecting unit including at least one of: a high voltage side noise detecting unit which detects high voltage side noise from brush noise included in the monitor voltage, based on whether a monitor voltage is larger than a first threshold voltage; and a low voltage side noise detecting unit which detects low voltage side noise from the brush noise included in the monitor voltage, based on whether the monitor voltage is smaller than a second threshold voltage; and a calculating unit which outputs the command signal to the motor controller to control the rotation number of the motor to reduce a occurrence number of the brush noise, based on at least one of the occurrence numbers.