In an embodiment of the invention, a package for high frequency waves mounted by a high frequency electronic circuit comprises an hermetic box-shaped high frequency package containing a high frequency electronic circuit in the inside and shielded by a conductor, an input terminal and an output terminal partly led out to the outside of the high frequency package, an input side feed-through section having one of its opposite ends connected to the input terminal and the other end connected to the high frequency electronic circuit and having a predetermined characteristic impedance; and an output side feed-through section having one of its opposite ends connected to the output terminal and the other end connected to the high frequency electronic circuit and having a characteristic impedance lower than the characteristic impedance of the input side feed-through section as viewed from the output terminal side. |