To provide a light source device capable of reducing production cost and operating cost.

The light source device (4) comprises a light generating chamber (6) in which a discharge electrode (8) is arranged, a gas inlet port (16) in which vacuum ultraviolet light generating gas that generates a vacuum ultraviolet light of a prescribed wavelength when the discharge electrodes (8, 43) discharge is introduced in the light generating chamber (6), a gas outlet port (17) from which the vacuum ultraviolet light generating gas introduced in the light generating chamber (6) is made to flow out of the light generating chamber (6), and circulation passages (21+22) which connect the gas outlet port (17) and the gas inlet port (16). The light source device (4) circulates the vacuum ultraviolet light generating gas flowing out of the gas outlet port (17) by introducing it into the light generating chamber (6) from the gas inlet port (16).