An antenna according to the present invention includes a dielectric layer 102 with an upper surface and a lower surface, a signal line strip 101 provided on the upper surface of the dielectric layer 102, and a grounding conductor portion 104 provided on the lower surface of the dielectric layer 102. The surface of the grounding conductor portion 104 includes a plurality of planar areas, each of which has a size that is shorter than the wavelength of an electromagnetic wave to transmit or receive. A distance from a virtual reference plane to each planar area is adjusted on an area-by-area basis. Thus, an antenna, which can change various antenna parameters such as radiation directivity, gain and efficiency dynamically and adaptively according to incessantly changing propagation environment of radio wave, is provided.