An LED power-source circuit includes an input filter circuit including noise prevention capacitors and a line filter, a diode bridge connected to the input filter circuit, a smoothing capacitor connected to an output of the diode bridge and having a capacitance of 1 μF or less, a DC-DC conversion circuit connected to the smoothing capacitor, and an LED assembly connected to an output of the DC-DC conversion circuit. Grounding capacitors are coupled to ground from an input power line between the line filter and the diode bridge. The total capacitance from the input power line to ground is set to be 1/200 or less of that of the smoothing capacitor.