PROBLEM TO BE SOLVED: To provide a structure formed so as to be able to uniformly irradiate an affected part by one time light irradiation by making illuminance of light from a window part uniform to materialize a wide irradiation region, in a light source device for medical care which is equipped with a light irradiation unit including an excimer lamp filled with xenon and chlorine and the window part for transmitting outgoing light from the excimer lamp.SOLUTION: An excimer lamp includes: a glass-made discharge container having paired rectangular planar faces extending parallel to each other, and paired lateral faces formed along side edge parts in a longitudinal direction of the paired rectangular planar faces and an external electrode provided in each of the paired rectangular planar faces of the discharge container. As to the excimer lamp, one of the rectangular planar faces is disposed while facing the window part in the inside of the light irradiation unit, and a longitudinal tube axis of the discharge container of the excimer lamp is almost vertically supported.
