A DC to DC converter includes an input terminal, an output terminal, first and second switches, an inductor, a smoothing unit, a first impedance element, a first resistor element, an operational amplifier and a control unit. The first switch is connected to the input terminal. The second switch is connected to the first switch and a ground terminal. The inductor is connected to the first switch and the output terminal. The smoothing unit is connected to the inductor and the ground terminal. The first impedance element is connected to the smoothing unit. The first resistor element is connected in series with the first impedance element. The operational amplifier is connected to the first impedance element. Reference voltage is added to the operational amplifier. The control unit controls the first and second switches according to a control signal outputted from the operational amplifier.