An antenna of this invention comprises an antenna element to which power is fed at a feed point; and a ground pattern that is juxtaposed with the antenna element and in which a tapered shape is formed with respect to the feed point of the antenna element. By providing the tapered shape for the ground pattern, it is possible to appropriately adjust the coupling degree with the antenna element, thereby it is possible to widen the bandwidth. Moreover, since the ground pattern and the antenna element are juxtaposed with each other, miniaturization can be achieved. When the antenna element is integrally formed in a dielectric substrate, further miniaturization can be achieved. Furthermore, when a cut-out portion is formed in the antenna element, the characteristic of the antenna in the low frequency range is improved.