In a laser produced plasma type extreme ultra violet light source apparatus, charged particles such as ions emitted from plasma can be efficiently ejected by the action of a magnetic field and secondary production of contaminants can be suppressed. The extreme ultra violet light source apparatus includes: a target nozzle for supplying a target material; a laser oscillator for applying a laser beam to the target material supplied by the target nozzle to generate plasma; an EUV collector mirror for collecting extreme ultra violet light radiated from the plasma; and an electromagnet for forming a magnetic field in a position where the laser beam is applied to the target material, wherein an aperture of the electromagnet is formed according to a shape of lines of magnetic flux of the magnetic field.