To miniaturize a high voltage applying unit in its axial direction as well as its diameter direction while maintaining withstand voltage properties of the unit.

This vacuum device is equipped with a vacuum vessel 2, an electrode 8 provided in the vacuum vessel 2, and the high voltage applying unit 4 provided on the outer wall 21 of the vacuum vessel 2 to apply a voltage to the electrode 8 from the outside. The high voltage applying unit 4 is equipped with a high voltage applying terminal 41 one end of which is provided on the atmosphere side, the other end of which is provided on the vacuum side, and the other end of which electrically makes contact with the electrode to apply the voltage, an insulator 42 having insulating properties through which the high voltage applying terminal passes, one end of which is provided on the atmosphere side, and the other end of which is provided on the vacuum side, and a flange part 43 through which the insulator 42 passes, and which is air-tightly attached to the outer wall 21 of the vacuum vessel. The outside periphery 42a of the insulator 42 projecting to the atmosphere side and the vacuum side from the flange part 43 is brought into a non-contact state, and also recessed and projecting parts are provided on the outside periphery 42a of the insulator 42.