A laser light shaping and wavefront controlling optical system 1 in accordance with an embodiment of the present invention comprises an intensity conversion lens 24 for converting and shaping an intensity distribution of laser light incident thereon into a desirable intensity distribution; an optical modulation device 34 for modulating the laser light emitted from the intensity conversion lens 24 so as to control a wavefront thereof; a condenser optical system 36 for converging the laser light issued from the optical modulation device 34; and an image-forming optical system 30, arranged between the optical modulation device 34 and the condenser optical system 36, having an entrance-side imaging plane between a plane 24x where the laser light emitted from the intensity conversion lens 24 attains the desirable intensity distribution and a modulation plane 34a of the optical modulation device 34 and an exit-side imaging plane on a pupil plane 36a of the condenser optical system 36.