To provide an inverted-F shaped antenna with ease of optimal matching.

A metallic flat plate 1, whose length is L1 and whose width is W1 placed horizontally at a position upward from a ground plate 4 by a distance D, is connected to another flat plate 10, in parallel with the flat plate 1 with a same size as the flat plate 1 via a vertical strip 6 whose length is L2 and whose width is W2 at a position from a ridge of the ground plate 4 by a distance D2. Then a feeding point exists in a coaxial end 12 connecting to the ridge of the strip 6 via a transmission line 11, and a short-circuit point is placed on the ridge 14 of the flat plate 1 via a coaxial connecting section 13 to obtain an optimum matching.