An EUV light source apparatus in which contamination or damage of optical elements and other component elements by debris can be suppressed to realize longer lives of them. The EUV light source apparatus is an apparatus for radiating extreme ultraviolet light by generating plasma of a target material within a chamber, and includes: a first laser unit for applying a first laser beam to the target material to generate pre-plasma; a second laser unit for applying a second laser beam to the pre-plasma to generate a main plasma for radiating the extreme ultraviolet light; and a magnetic field generating unit for generating a magnetic field within the chamber to control a state of at least one of the pre-plasma and the main plasma.