A motor drive apparatus for driving a motor includes a rectifier, a capacitor, an inverter circuit, a control portion arranged to output a drive signal, and a sensing portion arranged to sense a smoothed direct-current voltage, and output an analog sensing result to the control portion. After outputting a drive signal to drive the motor, the control portion quantizes the sensing result using a predetermined number of bits at a predetermined interval for a period longer than a power-supply period of an alternating-current power supply, determines Vn+1 which satisfies both Vn+1>Vn+2 and Vn+1>Vn to be a peak value when Vn denotes an nth voltage value obtained by quantizing the sensing result, determines whether the peak value is within a predetermined range, and outputs a drive signal to stop the motor if the peak value is outside of the predetermined range.