A charged particle beam device (1) includes a charged particle optical lens barrel (10), a support housing (20) equipped with the charged particle optical lens barrel (10) thereon, and an insertion housing (30) inserted in the support housing (20). A first aperture member (15) is disposed in the vicinity of the center of the magnetic field of an objective lens, and a second aperture member (15) is disposed so as to externally close an opening part provided at the upper side of the insertion housing (30). Further, when a primary charged particle beam (12) is irradiated to a sample (60) arranged under the lower side of the second aperture member (31), secondary charged particles thus emitted are detected by a detector (16).