A light source device includes a light emitting element emitting light of a first wavelength band, a fluorescent wheel, a dichroic mirror, a reflection member and a polarization conversion element. The fluorescent wheel includes a fluorescent area converting the light of the first wavelength band into fluorescent light and a transmission area transmitting the light of the first wavelength band. The dichroic mirror reflects the light of the first wavelength band a first polarization direction, transmits the light in a second polarization direction, and transmits or reflects the fluorescent light. The reflection member reflects the light transmitted through the transmission area toward the transmission area. The polarization conversion element is disposed between the fluorescent wheel and the reflection member, transmits the lights transmitted through the transmission area and reflected by the reflection member, and converts the light in the first polarization direction into the second polarization direction.