<p>A semiconductor light source lighting circuit (100) is provided with: a switching regulator (104) that generates a drive current (I LED ) of a semiconductor light source (40) using a switching element (122); and a control circuit (102) that controls ON/OFF of the switching element (122). The control circuit (102) is provided with: a comparator (116) that compares the drive current (I LED ) and a target value; a counter (118) that counts a digital value in a count direction determined by a comparison result of the comparator (116); a digital-analog converter (120) that converts the digital value into an analog signal; and a drive circuit (106) that controls the ON/OFF of the switching element (112) based on the analog signal. The counter (118) counts the digital value at a speed determined by an ON/OFF cycle of the switching element (122).</p>
