[Problem]An extreme ultraviolet light source device in accordance with the present invention corrects an optical performance of a laser beam in an appropriate manner.[Means for Resolution]A guide laser beam that has an optical axis and a beam diameter substantially equivalent to those of a driver pulsed laser beam is introduced into an amplification system 30 that amplifies a laser beam that is output from a driver laser oscillator 20. The guide laser beam is output from a laser device 50 as a continuous light, and is introduced into a light path of the driver pulsed laser beam via a guide laser beam introduction mirror 52. A sensor 44 detects an angle (a direction) of a laser beam and a variation of a curvature of a wave front. A wave front correction controller 60 outputs a signal to a wave front correction part 34 based on a measured result of a sensor 36. The wave front correction part 34 corrects a wave front of a laser beam to be a predetermined wave front according to an instruction from the wave front correction controller 60.