Disclosed is a laser processing device. The laser processing device includes a laser beam source irradiating a laser beam, and a laser processing head. The laser processing head includes a transmitting window through which the laser beam passes, an aperture formed in a bottom of the laser head and allowing the laser beam to pass through via the transmitting window, an introducing hole introducing a gas into the laser processing head, and an exhausting hole discharging a gas in the laser processing head to outside. The laser processing head further includes a air hole introducing the gas to the periphery of the laser irradiating area, an air hole allowing to discharge the ambient gas of the laser irradiating area, and a masking shield having an opening placed between the transmitting window and the aperture, and an aerating portion communicated with the introducing hole and exhausting hole.