A dimming lighting circuit includes: a rectifier circuit; a phase detection circuit which outputs a dimming signal having a signal level corresponding to a conduction phase angle of an AC voltage; and a DC-DC converter which receives a DC voltage output from the rectifier circuit and supplies a light source with a DC current corresponding to the signal level of the dimming signal output from the phase detection circuit. If the conduction phase angle detected when the dimming lighting circuit receives the AC voltage at power-on is less than or equal to a predetermined angle, the phase detection circuit outputs, as the dimming signal, a substitute signal having a signal level corresponding to a conduction phase angle greater than the conduction phase angle of the AC voltage, for a predetermined time period.