An RF package includes a multilayered dielectric substrate, a feed-through, and metal members. First and second dielectric substrates are formed on the multilayered dielectric substrate. The multilayered dielectric substrate has a cavity where a semiconductor element is to be mounted. The feed-through connects the inside and outside of the cavity and is comprised of a coplanar line formed on the first dielectric substrate and an inner layer line obtained by forming the second dielectric substrate on the coplanar line. The coplanar line and the inner layer line share a strip-like signal conductor. The metal members are formed at a connection interface between the coplanar line and the inner layer line on two sides of the signal conductor.