An instrument producing a charged particle beam according to the present invention is provided with: a charged particle source; a plurality of first electrodes disposed along a direction of irradiation of charged particles from the charged particle source; a plurality of insulation members disposed between the first electrodes; and a housing mounted around the plurality of first electrodes. The housing is formed from an insulating solid material, and includes a plurality of second electrodes disposed at positions in proximity to the plurality of first electrodes. At least one of the plurality of second electrodes is electrically connected to at least one of the plurality of first electrodes, each of the plurality of second electrodes having the same potential as the potential of the proximate one of the first electrodes.