Solid tin (Sn) is used as a target, a CO2 laser is used as an excitation source for the target, and after the size of debris emitted from plasma is decreased to a nanometer or smaller size by exciting the solid tin by a laser beam outputted from the CO2 laser, the emitted debris of a nanometer or smaller size is acted upon so as not to reach the optical element. In accordance with the present invention, in the EUV light source apparatus, the debris emitted together with EUV light from plasma generated by exciting a target within a chamber by a laser beam is prevented from adhering to an optical element provided within the chamber and forming a metal film. As a result, the service life of the optical element can be extended.