To provide a light source device suitable for request of miniaturization in which emitted light of a lamp can be efficiently used.

The concave reflection mirror 20 of the light source device has an anterior elliptical mirror 21 and a posterior elliptical mirror 23; the light reflected by the anterior elliptical mirror 21 forms an illumination distribution of a doughnut shape; and the light reflected by the posterior elliptical mirror 23 forms an illumination distribution of a doughnut shape where the illumination distributions are adjacently formed, when the light reflected by the anterior elliptical mirror 21 and the light reflected by the posterior elliptical mirror 23 are irradiated together, on an incident surface 31 of an optical element 30 initially arranged ahead of the concave reflection mirror 20.

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