Vacuum capacitor

The present invention can easily adjust capacitance of a vacuum capacitor while maintaining a vacuum state in a vacuum chamber of the vacuum capacitor. A fixed electrode 4 is formed by arranging a plurality of flat electrode members 5 in layers at a certain distance in an axial direction of a vacuum chamber 1b. A movable electrode 7 is formed by arranging a plurality of flat electrode members 8 in layers at a certain distance in the axial direction of the vacuum chamber 1b and fixing the electrode members 8 to a movable electrode shaft 9. By rotation of the movable electrode shaft 9, each electrode member 8 is inserted into and extracted from a gap between the electrode members 5 of the fixed electrode 4 in noncontact with the electrode members 5 of the fixed electrode 4. A magnetic flux receiving portion 106b is fixed to a seal member 102 side of a disk member 106a that is provided at the movable electrode shaft 9. A magnetic flux generating unit 104 provided at a capacitance control unit 14 is arranged in a direction parallel to the movable electrode shaft 9 with respect to the magnetic flux receiving portion 106b. By rotating the capacitance control unit 14 also rotating the magnetic flux receiving portion 106b by magnetic attraction of the magnetic flux generating unit 104, an overlap area of the movable electrode 7 with respect to the fixed electrode 4 is changed, capacitance is then adjusted.