In a wall of a package base made of aluminum or aluminum alloy, there is formed a through-hole, through which a semi-rigid coaxial cable passes. A central conductor of the semi-rigid coaxial cable is joined to an electrode with a solder material. The semi-rigid coaxial cable has an insulating material through which the central conductor passes and an outer conductor provided therearound. The central conductor and outer conductor are made of stainless steel, for example, and the insulating material is made of fluororesin, for example. Inside the through-hole, the wall of the package base and the outer conductor are electrically connected to each other via a stainless material within the hole formed in a cylindrical fluororesin material. The semi-rigid coaxial cable and the like are fixed to the wall with a conductive screw.