An EUV (Extreme Ultra Violet) light source device ionizes a target material in an ionizer, and supplies the ionized target material to a point of generating a plasma. This reduces the generation of debris. The ionizer simultaneously irradiates laser beams of plural wavelengths corresponding to the excited level of tin on a target material to ionize the target material. The ionized target material is extracted from the ionizer with a high voltage applied from an ion beam extractor, and accelerated and supplied to a plasma generation chamber. When driver laser beam is irradiated on the ionized target material, a plasma is generated, thereby emitting EUV radiation.