To provide a semiconductor element housing package which is capable of improving the lead terminals in properties of transmitting high-frequency signals and to provide a semiconductor device.

The semiconductor element housing package is equipped with a resin base 1 where a mount 1b on which a semiconductor element 4 is mounted is formed on the bottom of a recessed part 1a formed on its top surface, and a plurality of lead terminals 2 which are provided so as to penetrate through the side wall 1c of the base 1. The lead terminals 2 are each composed of a lead terminal 2a for transmitting high-frequency signals and two grounding lead terminals 2b which are equally separate from the lead terminal 2a and located on its lateral sides. The high-frequency signal transmitting lead terminal 2a is equipped with a wide part 2d which is located inside the side wall 1c and gradually expanded in the width toward the outside of the base 1.