A lighting device that lights up an LED and includes a DC power source, a buck converter and a control circuit. The buck converter includes a switching element, an inductor and a diode. The control circuit includes a current detection circuit that detects an electric current flowing through the switching element, a voltage detection circuit that detects a voltage across the inductor, a delay circuit that generates a delay time according to the voltage detected by the voltage detection circuit, and a drive circuit that generates and outputs a control signal to the switching element, the control signal turning OFF the switching element after a lapse of the delay time generated by the delay circuit from when the electric current detected by the current detection circuit reaches a predetermined current command value.