A laser irradiation device having a laser oscillator that generates a laser beam; a laser irradiation head that performs laser processing by directing a laser beam generated by said laser oscillator onto a region to be processed; and a transmission mechanism that gets said laser beam through emitted from said laser oscillator to said laser irradiation head, wherein said laser irradiation head comprises: (a) a laser beam adjustment unit that produces a laser beam directed onto said region to be processed by adjusting said laser beam from said transmission mechanism; (b) a protective glass window arranged in an emission region that emits said laser beam of said irradiation head onto said region to be processed; (c) a reflection mechanism, provided within said irradiation head, (d) an image pickup camera and (e) an image adjustment optical system, provided between said reflection mechanism and said image pickup camera, whereby a focal point position of said image pickup camera can be changed over to a position of at least said protective glass window and said region to be processed, characterized in that said reflection mechanism gets said laser beam through and reflects at least visible light, of reflected lights from said region to be processed, said reflection mechanism comprising a dichroic mirror arranged on an optical path of said laser beam got through from said transmission mechanism to said protective glass window, and wherein said dichroic mirror is equipped with a drive mechanism and is capable of being set in a position in which said dichroic mirror reflects visible light that is incident from a side of said protective glass window and a position in which said dichroic mirror reflects visible light that is incident from a side of said laser beam adjustment unit; and said image pickup camera inputs said light reflected by said reflection mechanism. a laser oscillator that generates a laser beam; a laser irradiation head that performs laser processing by directing a laser beam generated by said laser oscillator onto a region to be processed; and a transmission mechanism that gets said laser beam through emitted from said laser oscillator to said laser irradiation head, (a) a laser beam adjustment unit that produces a laser beam directed onto said region to be processed by adjusting said laser beam from said transmission mechanism; (b) a protective glass window arranged in an emission region that emits said laser beam of said irradiation head onto said region to be processed; (c) a reflection mechanism, provided within said irradiation head, (d) an image pickup camera and (e) an image adjustment optical system, provided between said reflection mechanism and said image pickup camera, whereby a focal point position of said image pickup camera can be changed over to a position of at least said protective glass window and said region to be processed, characterized in that said reflection mechanism gets said laser beam through and reflects at least visible light, of reflected lights from said region to be processed, said reflection mechanism comprising a dichroic mirror arranged on an optical path of said laser beam got through from said transmission mechanism to said protective glass window, and wherein said dichroic mirror is equipped with a drive mechanism and is capable of being set in a position in which said dichroic mirror reflects visible light that is incident from a side of said protective glass window and a position in which said dichroic mirror reflects visible light that is incident from a side of said laser beam adjustment unit; and said image pickup camera inputs said light reflected by said reflection mechanism.