According to one embodiment; an antenna device according to this embodiment includes the first antenna element formed from a folded monopole element and a capacitor element. The first antenna element has a first end connected to a feeding terminal, a second end connected to the first ground terminal, and a middle portion folded, with a stub being provided between the forward portion and backward portion formed by this folding. The capacitor element is inserted between the stub and the above feeding terminal of the forward portion of the first antenna element.