A light source device (1, 66) comprising a semiconductor light source capable of emitting light in a blue wavelength range and a fluorescent wheel (2, 60, 61, 63, 64, 65) having an incident surface on which light emitted from the semiconductor light source is incident, wherein the fluorescent wheel (2, 60, 61, 63, 64, 65) includes a support substrate rotatable about a rotation axis (Ax) and having the incident surface provided with a plurality of segment regions containing a fluorescent material; and wherein the support substrate is formed of a metal material having a reflective flat surface on a side of the incident surface; characterized in that the plurality of segment regions includes at least a first segment region consisting only of a first fluorescent material layer and a second segment region that is a laminated film of a second fluorescent material layer on the first fluorescent material layer, the first segment region and the second segment region being alternately provided in the circumferential direction about the rotation axis (Ax); the first fluorescent material layer is configured such that a first fluorescent material that receives the light emitted from the semiconductor light source as excitation light and emits yellow light is dispersed in a resin binder; the second fluorescent material layer is configured such that a second fluorescent material that receives the light emitted from the semiconductor light source as excitation light and emits red light is dispersed in a resin binder; the second fluorescent material is a fluorescent material that emits light also by being excited by the yellow light emitted from the first fluorescent material and has a higher emission quantum yield when the yellow light emitted from the first fluorescent material is used as the excitation light than when the light emitted from the semiconductor light source is used as the excitation light; and the light emitted from the semiconductor light source is incident on the incident surface of the fluorescent wheel (2, 60, 61, 63, 64, 65) in an irradiation region of which width in a radial direction around the rotation axis (Ax) is smaller than a width of the first fluorescent material layer. wherein the fluorescent wheel (2, 60, 61, 63, 64, 65) includes a support substrate rotatable about a rotation axis (Ax) and having the incident surface provided with a plurality of segment regions containing a fluorescent material; and wherein the support substrate is formed of a metal material having a reflective flat surface on a side of the incident surface; characterized in that the plurality of segment regions includes at least a first segment region consisting only of a first fluorescent material layer and a second segment region that is a laminated film of a second fluorescent material layer on the first fluorescent material layer, the first segment region and the second segment region being alternately provided in the circumferential direction about the rotation axis (Ax); the first fluorescent material layer is configured such that a first fluorescent material that receives the light emitted from the semiconductor light source as excitation light and emits yellow light is dispersed in a resin binder; the second fluorescent material layer is configured such that a second fluorescent material that receives the light emitted from the semiconductor light source as excitation light and emits red light is dispersed in a resin binder; the second fluorescent material is a fluorescent material that emits light also by being excited by the yellow light emitted from the first fluorescent material and has a higher emission quantum yield when the yellow light emitted from the first fluorescent material is used as the excitation light than when the light emitted from the semiconductor light source is used as the excitation light; and the light emitted from the semiconductor light source is incident on the incident surface of the fluorescent wheel (2, 60, 61, 63, 64, 65) in an irradiation region of which width in a radial direction around the rotation axis (Ax) is smaller than a width of the first fluorescent material layer.