The lighting device in accordance with the present invention includes: a switching regulator including a switching element and an inductor and configured to supply a direct current to a DC light source; a control circuit unit for controlling the switching element in accordance with a dimming signal for determining an on period in which the DC light source is kept turned on and an off period in which the DC light source is kept turned off to adjust luminance of the DC light source; a current detection unit configured to output a detection value indicative of a current flowing through the inductor; and a superimposing circuit unit. The circuit control unit, in the on period, turns off the switching element when an input value received via the input terminal for receiving the detection value exceeds a first threshold, and turns on the switching element when the input value falls below a second threshold, and keeps turning off the switching element in the off period. The superimposing circuit unit is configured to keep the input value not less than the second threshold in the off period.