A semiconductor light source lighting circuit includes a voltage step-down unit configured to generate a drive voltage lower than an input voltage by turning on or off a first switching element in a voltage step-down mode, a voltage step-up unit configured to generate the drive voltage higher than the input voltage by turning on or off a second switching element in a voltage step-up mode, and a controller. The controller includes a charge pump unit configured to repeat charging from the drive voltage to a second capacitor and discharging from the charged second capacitor to the first capacitor in the voltage step-up mode, and a switch drive unit configured to apply a voltage higher than the voltage at the other end of the first switching element to the control terminal of the first switching element by using a voltage of the charged first capacitor.