Abstract: A laser beam shaping device is made up of a multiple reflecting mirror unit with reflecting surfaces facing each other to reflect a laser beam in multiple reflections, a light gathering cylindrical lens for gathering the laser beam near the inlet of the multiple reflecting mirror unit, a spherical lens for focusing the laser beam emerging from the multiple reflecting mirror unit, and a beam width setting cylindrical lens for setting the width of the laser beam in the direction which is perpendicular to the direction of advance of the laser beam and parallel with the reflecting surfaces of the multiple reflecting mirror unit, whereby, in shaping a laser beam, the energy loss of the laser beam is minimized, and the laser beam is made uniform in energy distribution, and the laser beam can be changed in configuration and dimension according to the contents of a laser beam machining operation.