To effectively cool each light source element in a lamp unit with a plurality of light source elements arrayed in one direction, and structured by arranging a plurality of the light source element rows in accordance with the need.

The lamp unit is structured by arraying a plurality of light source elements 12 each structured of a short-arc lamp 14 and a reflector 15. An air intake member 17 having air intake ports 17a, 17b is fitted on a light emission opening side of the reflector 15, an air inflow port 103f is fitted at an explosion-proof plate fixing wall part 103, air taken in from the air inflow port 103f is flown into the reflector 15 through the air intake ports 17a, 17b to cool the lamp 14. Further, an air inflow port 103h is fitted at the explosion-proof plate fixing wall part 103, air taken in from the air inflow port 103h is flown to an outer surface of the reflector 15 through air intake ports 102d, 102e fitted to a top plate part 102b and a bottom plate part 102c to cool the reflector 15 and a reflector base 16.