A light source device comprising: a light-emitting section (11, 21) including a plurality of light-emitting elements, wherein each of the plurality of light-emitting elements includes a light-emission control thyristor and a surface emitting element (VCSEL) connected in series with the light-emission control thyristor; a shifter (12, 22) including a plurality of shift thyristors and either a plurality of coupling transistors or a plurality of coupling diodes, wherein the plurality of shift thyristors and the plurality of coupling transistors or coupling diodes are respectively connected to each other, wherein the plurality of light-emitting elements are connected to the shifter, wherein the shifter is configured to perform a shift operation, by controlling one of the plurality of shift thyristors (T) to be turned ON, so as to turn ON a corresponding one of the plurality of coupling transistors or coupling diodes and to shift a next one of the plurality of shift thyristors (T) to a state in which the next one of the plurality of shift thyristors (T) is able to be turned ON, subsequently controlling the next one of the plurality of shift thyristors (T) to be turned ON, and subsequently controlling the one of the plurality of shift thyristors (T) to be turned OFF; and a controller configured to cause the shifter to perform the shift operation to set, among the plurality of light-emitting elements, a light-emitting element which is to emit light by controlling a corresponding one of the plurality of shift thyristors (T) to be turned ON, wherein the set light-emitting element (VCSEL, S) is configured to be shifted to a state in which the set light-emitting element is able to emit light when the corresponding one of the plurality of shift thyristors (T) is turned ON, the light source device being characterized in that the controller is further configured to change the shifter to an OFF state after the set light-emitting element is shifted to a state in which the set light-emitting element is able to emit light, and to cause the set light-emitting element to emit light a plurality of times by turning ON and OFF a voltage application side of a power source, the power source supplying a light-emitting current which causes the light-emitting element to emit light. a light-emitting section (11, 21) including a plurality of light-emitting elements, wherein each of the plurality of light-emitting elements includes a light-emission control thyristor and a surface emitting element (VCSEL) connected in series with the light-emission control thyristor; a shifter (12, 22) including a plurality of shift thyristors and either a plurality of coupling transistors or a plurality of coupling diodes, wherein the plurality of shift thyristors and the plurality of coupling transistors or coupling diodes are respectively connected to each other, wherein the plurality of light-emitting elements are connected to the shifter, wherein the shifter is configured to perform a shift operation, by controlling one of the plurality of shift thyristors (T) to be turned ON, so as to turn ON a corresponding one of the plurality of coupling transistors or coupling diodes and to shift a next one of the plurality of shift thyristors (T) to a state in which the next one of the plurality of shift thyristors (T) is able to be turned ON, subsequently controlling the next one of the plurality of shift thyristors (T) to be turned ON, and subsequently controlling the one of the plurality of shift thyristors (T) to be turned OFF; and a controller configured to cause the shifter to perform the shift operation to set, among the plurality of light-emitting elements, a light-emitting element which is to emit light by controlling a corresponding one of the plurality of shift thyristors (T) to be turned ON, wherein the set light-emitting element (VCSEL, S) is configured to be shifted to a state in which the set light-emitting element is able to emit light when the corresponding one of the plurality of shift thyristors (T) is turned ON, the light source device being characterized in that the controller is further configured to change the shifter to an OFF state after the set light-emitting element is shifted to a state in which the set light-emitting element is able to emit light, and to cause the set light-emitting element to emit light a plurality of times by turning ON and OFF a voltage application side of a power source, the power source supplying a light-emitting current which causes the light-emitting element to emit light.