To provide a high-frequency unit shielding structure which is small in number of parts, easily assembled, and capable of surely shielding the high-frequency unit.

A case 2 which houses a board 1, where a circuit that generates high-frequency signals is formed, is composed of a main body 3, a lid 4, and shielding members 5 and 6. A housing part 9 is opened inside the opening edge face 7 of the main body 3 through the intermediary of an opening 8. A stepped part 10 is located inside the opening 8. The lid 4 is equipped with a shielding projection 12, which is inserted into the opening 8 and a lid part 11. A board 1 is placed on the stepped part 10, the shielding members 5 and 6 are placed, and the opening 8 of the main body 3 is closed with the lid 4 to fix them. The shielding projection 12 is inserted into the opening 8 to pinch the board 1 between itself and the stepped part 10, so that the board 1 is held surely to produce no gaps between the component parts. The edge faces of the board 1, where high-frequency waves are liable to leak out, are not located on the same plane with a joint between the lid 4 and main body 3. The shielding member 5 is a double structure. High-frequency waves hardly leak out of this shielding structure due to the synergistic effects of these constitutions.