PURPOSE: To eliminate a sliding part to provide a stable electric connection by employing a flexible connector to connect a plunger of a tuning device with a cavity main body.

CONSTITUTION: A plunger type tuner is provided for regulating a resonance frequency and a flexile connector 9 is arranged between a plunger 2 and a cavity main body 1. The flexible connector 9 is composed of a plurality of plate springs and the like and connected to a periphery of the plunger 2 as well as to a flange side via a connecting plate 10. When the plunger 2 moves, the flexible connector 9 maintains a connection between the cavity main body 1 and the plunger 2, without sliding but being deformed, so as to feed a high frequency electric current. A high frequency electromagnetic wave is prevented from entering by the high frequency electric current flowing through the flexible connector 9 and leakage to a bellows 5 side is decreased to prevent overheating of the bellows 5. According to this constitution, a sliding part is eliminated and a stable electric connection can be performed.