A light source module includes a light emitting element having a resonator formed of a photonic crystal structure, and a polarization conversion element, wherein the polarization conversion element includes a polarization split layer that reflects first polarized light toward a first direction, and transmit second polarized light toward a second direction, a reflecting layer that reflects the first polarized light, toward the second direction, and a retardation layer which is disposed in a light path of one of the first polarized light and the second polarized light, and converts the one of the first polarized light and the second polarized light into another of the first polarized light and the second polarized light, the resonator has a resonant part, and in a plan view, a length of the resonant part in the first direction is shorter than a length of the resonant part in a third direction perpendicular to the first direction and the second direction.