To provide a compact gunn diode oscillator provided with a shield container which seals a gunn diode and micro-strip lines to prevent invasion of steam.

A surface signal electrode and a back signal electrode are connected through a first via hole that penetrates from a plane board surface to the back, and a first surface bias electrode and a first back bias electrode are connected through a second via hole. A surface ground electrode and a back ground electrode are connected through a third via hole, and the back signal electrode and the first back bias electrode are constituted of a bump electrode. In addition, the plane board surface is sealed into the shield container.