There is provided a device for generating a lossless pulse ultraviolet laser beam of generating a laser beam having a desired wavelength by repeatedly rotating a laser beam generated by a pulse ytterbium fiber laser several times. The device includes a pulse ytterbium fiber laser generating and emitting a laser beam of a high-speed pulse form, a nonlinear harmonic crystal for modulating a wavelength of the laser beam into a desired wavelength, a lens for focusing the modulated beam, a reflecting mirror for transmitting a beam having a desired wavelength and reflecting a beam having an undesired wavelength, and a laser window having one AR-coated surface.