The apparatus for irradiating a laser in accordance with an exemplary embodiment includes: a main body; a laser resonator located within the main body and configured to generate a laser beam and output the laser beam forwards; a beam barrel in which a focusing lens is fixed; a beam barrel guiding unit located in front of the main body and configured to guide forward and backward movement of the beam barrel; and a forward and backward moving means connected to an outer periphery of the beam barrel and configured to move the beam barrel forwards and backwards relative to an irradiation target portion in front of the beam barrel. A screw thread is formed on the outer periphery of the beam barrel and a screw thread is formed on an inner surface of the forward and backward moving means.