PURPOSE: To facilitate the packaging of other parts on the periphery of a micro wave oscillator by reducing the protrution of the head of an adjustment rod by means of adjustment.

CONSTITUTION: The adjustment rod for adjusting an oscillation frequency is divided into an adjustment rod 2 and an adjustment rod 3, and they are connected by screw structure. The adjustment rod 2 is fitted to a casing 1 so that it can be rotated, and the adjustment rod 3 is fixed to a supporting board 4. The supporting board 4 is a rotation stopper having the same size as the internal size of the oscillator case 1. Since a metallic board 5 for adjusting the oscillation frequency is fixed to the opposite surface of the supporting board 4, a space between the metallic board 5 and the dielectric oscillator 6 can be adjusted without causing the head of the adjustment rod 2 to protrude by rotating the adjustment rod 2.