PROBLEM TO BE SOLVED: To assure safety of eyes to excitation light while efficiently entering both excitation light and white light to a light guide.SOLUTION: The light source device is configured such that a second light (e.g., excitation light) is diffusively or convergently entered to an optical system 56 to which first and second lights differed in wavelength band are entered and which causes the first and second lights incident on an incident end surface 60 of a light guide portion LG, with the first light (e.g., white light) being collectively entered into the area of the incident end surface of the light guide portion LG by the optical system 56, whereby the second light transmitted by the optical system 56 is prevented from being converged to one point on the incident end surface 60 of the light guide portion LG, and the second light is collectively entered into the area of the incident end surface 60 of the light guide portion LG.
