A light source device of the present invention includes: an excitation light source (1a) configured to emit irradiation light of a color component to be used as excitation light and projection light; a fluorescent member (5) disposed in an excitation light path (X2) and configured to generate fluorescence of a color component different from the color component of the irradiation light when being irradiated with the irradiation light; a light path merger unit configured to merge a fluorescence light path (X3) through which the fluorescence generated with irradiation of the irradiation light is delivered, and a projection light path (X1) through which the projection light is delivered; and a light path switch disk (3) configured to switch the irradiation light between the excitation light path (X2) and the projection light path (X1).