A lighting circuit comprising: a voltage conversion unit which is configured to receive a DC voltage to perform voltage conversion and to supply a drive current to a light source unit which includes a plurality of light emitting elements (30-1 - 30-n) connected in series; a bypass path (BP1 to BPn) which includes a plurality of bypass switches (15-1 - 15-n) each of which is connected in parallel with a respective one of the light emitting elements (30-1 - 30-n) and are connected in series; and a control unit which is configured to control the voltage conversion unit through a converter drive unit comprised in the lighting circuit and the plurality of bypass switches (15-1 - 15-n), the control unit being configured to perform constant current control of the drive current (Id), characterized in that the control unit is configured to, when receiving an all turning-off instruction of the light source unit, turn on all of the bypass switches (15-1 - 15-n) and leading the drive current (Id) to all of the bypass switches (15-1 - 15-n), thereby turning off all of the plurality of light emitting elements (30-1 - 30-n), from a state where all or part of the light emitting elements (30-1 - 30-n) are on, by carrying out the following sequential steps: confirming if all of the bypass switches (15-1 - 15-n) are turned on; waiting for a second predetermined time; turning off all the bypass switches (15-1 - 15-n) if a turning-on instruction is received before the second predetermined time elapses; instructing the converter drive unit to stop operating via a control signal after the second predetermined time elapses. a voltage conversion unit which is configured to receive a DC voltage to perform voltage conversion and to supply a drive current to a light source unit which includes a plurality of light emitting elements (30-1 - 30-n) connected in series; a bypass path (BP1 to BPn) which includes a plurality of bypass switches (15-1 - 15-n) each of which is connected in parallel with a respective one of the light emitting elements (30-1 - 30-n) and are connected in series; and a control unit which is configured to control the voltage conversion unit through a converter drive unit comprised in the lighting circuit and the plurality of bypass switches (15-1 - 15-n), the control unit being configured to perform constant current control of the drive current (Id), characterized in that the control unit is configured to, when receiving an all turning-off instruction of the light source unit, turn on all of the bypass switches (15-1 - 15-n) and leading the drive current (Id) to all of the bypass switches (15-1 - 15-n), thereby turning off all of the plurality of light emitting elements (30-1 - 30-n), from a state where all or part of the light emitting elements (30-1 - 30-n) are on, by carrying out the following sequential steps: confirming if all of the bypass switches (15-1 - 15-n) are turned on; waiting for a second predetermined time; turning off all the bypass switches (15-1 - 15-n) if a turning-on instruction is received before the second predetermined time elapses; instructing the converter drive unit to stop operating via a control signal after the second predetermined time elapses. confirming if all of the bypass switches (15-1 - 15-n) are turned on; waiting for a second predetermined time; turning off all the bypass switches (15-1 - 15-n) if a turning-on instruction is received before the second predetermined time elapses; instructing the converter drive unit to stop operating via a control signal after the second predetermined time elapses.