High-voltage insulating structure, charged particle gun, and charged particle beam device

A high-voltage insulating structure in which an electrically conductive part, to which a high voltage is applied and which extends in an axial direction, is surrounded by an insulator, wherein

• the insulator includes a first insulator, a second insulator positioned on the opposite side from the first insulator in the axial direction, and a third insulator positioned between first and second insulators,
• an electrical resistivity of the third insulator is smaller than electrical resistivities of the first and second insulators, and
• as for a thickness of the third insulator in the axial direction, a first thickness at an outer side farther from the electrically conductive part is less than a second thickness at an inner side closer to the electrically conductive part.