In an EUV light source apparatus, a collector mirror is protected from debris damaging a mirror coating. The EUV light source apparatus includes: a chamber in which extreme ultraviolet light is generated a target supply unit for supplying a target material into the chamber a plasma generation laser unit for irradiating the target material within the chamber with a plasma generation laser beam to generate plasma an ionization laser unit for irradiating neutral particles produced at plasma generation with an ionization laser beam to convert the neutral particles into ions a collector mirror for collecting the extreme ultraviolet light radiated from the plasma and a magnetic field or electric field forming unit for forming a magnetic field or an electric field within the chamber so as to trap the ions.
