To effectively cool a light-emitting section in the surrounding of a cathode of a lamp in a light source element used for a lamp unit wherein a plurality of light source elements are lined up in one direction and a plurality of light source element rows are arranged as the need arises.

In the light source element including a short arc type lamp, and a reflector for reflecting light of the lamp, the light source element has an air intake member arranged on a light emitting opening side of the reflector and preparing a first air intake port for flowing an air inside the reflector. An electrode located on a light emitting side of the lamp is arranged on an extension line of a straight line for connecting respective centers of an upper end edge and a lower end edge of the first air intake port in the cross-section wherein the light source element is cut with a plane containing an optical axis of the reflector.