PROBLEM TO BE SOLVED: To enhance the axis adjustment operability of a charged particle beam in a charged particle beam irradiation device, and to enhance the accuracy thereof.SOLUTION: A charged particle beam irradiation device 100 includes a beam source 101 for emitting a charged particle beam, an aperture plate 103a having an aperture 130, a deflection unit 102 for deflecting the charged particle beam, a control unit 110 for scanning the deflection unit 102 with the charged particle beam, in a scanning range wider than the aperture 130 above the aperture plate 103a, a detector 140 provided insertably on an axis passing through the beam source 101 and the center of the aperture 130, and detecting passage of the deflected charged particle beam through the aperture 130, a beam position extraction unit 141 for determining the centroid position of a region of the charged particle beam passed through the aperture 130 in the scanning range, and a correction unit 142 for determining the current amount supplied to t
