Shielding of high-frequency circuits is achieved using a simple and inexpensive configuration not using any lid. A high-frequency circuit mounting substrate (20) is disposed, on an underside surface layer of which are disposed high-frequency circuits (21 and 22) and is formed a first grounding conductor that has same electric potential as grounding conductors of the high-frequency circuits and that surrounds the high-frequency circuits. A mother control substrate (3) is disposed, on which the high-frequency circuit mounting substrate (20) is mounted in such a way that the high-frequency circuits are sandwiched therebetween and on which a second grounding conductor is formed in a region facing the high-frequency circuits. Plural first lands are formed on the first grounding conductor of the high-frequency circuit mounting substrate (20) to surround the high-frequency circuits. Plural second lands are formed that are electrically connected to the second grounding conductor at positions on a surface layer of the mother control substrate (3) which face the first lands. Plural solder balls (30G2) are disposed for connecting the first lands and the second lands. The high-frequency circuits are housed in pseudo shielding cavities surrounded by the solder balls (30G2), the grounding conductors of the high-frequency circuits, and the first and second grounding conductors.