Abstract: A powder bed fusion additive manufacturing (PBF-AM) apparatus includes an electron gun chamber, a build chamber, a first vacuum pump, a second vacuum pump, and a beam path. In addition, the three-dimensional PBF-AM apparatus includes a differential evacuation aperture, a focusing lens, and an axis adjustment mechanism. The differential evacuation aperture divides an internal space of the beam path into two, and has a restriction hole through which an electron beam can pass. The focusing lens is configured to focus the electron beam by a restriction hole of the differential evacuation aperture. The axis adjustment mechanism is configured to adjust a trajectory of the electron beam or positions of the focusing lens and the differential evacuation aperture so that an optical axis of the electron beam passes through both the center of the restriction hole and the center of the focusing lens.