To prevent dielectric breakdown caused by a hole edge part form of a bushing mounting hole provided on a casing of a high voltage switch, increase a breakdown voltage of the high voltage switch, and achieve miniaturization and cost reduction of the high voltage switch with the reference of the breakdown voltage.

A high voltage switch is provided with a casing 1, bushings 2 mounted through side walls 10, 11 on both sides of it, and lead-out wires connected to the bushings and an operation handle. In the side walls 10, 11 on both sides of the casing 1, bushing mounting holes 12, 13 for mounting bushings 2 formed of insulators are provided through. The bushing mounting holes 12, 13 are formed by burring work, and their hole edge parts 120, 130 are formed with curvature. Outer side parts continuous with the hole edge parts 120, 130 are formed cylindrical with shorter depth. The bushings 2 are mounted on the bushing mounting holes 12, 13 respectively.