A light source device includes an optical element 22 having a first face 1 opposed to a solid light emitting element 21. The optical element 22 includes second and third faces 2, 3 opposing in parallel to each other and both substantially perpendicular to the first face 1, a fourth face 4 substantially perpendicular to the second and third faces 2, 3 and also obliquely-opposed to the first face 1 and a fifth face 5 as an exit face. The fifth face 5 has an area smaller than an area of a light emitting face of the solid light emitting element 21. The light source device further includes a polarization converting element 42 having an incident surface opposing in substantially-parallel to the fifth face 5 through a space, polarization separating elements 43 for separating incident light from the optical element 22 in polarization, a first reflecting surface 45 for reflecting one of polarization-separated fluxes and wave plates 44 for converting either of phases of the polarization-separated fluxes.