A light source device includes at least one discharge tube, a discharge medium sealed inside the discharge tube, and first and second electrodes for exciting the discharge medium. The first electrode is arranged inside the discharge tube. The second electrode is in contact with an outer surface of the discharge tube at a plurality of linear contact portions. The plurality of linear contact portions are substantially parallel with each other. Thus, a light source device is provided in which the occurrence of constricted discharge can be suppressed readily.