An object of the present invention is to obtain high radiation efficiency by strengthening electromagnetic coupling in an antenna device that supplies a radiation current by the electromagnetic coupling. An antenna device includes a substrate 110 and a conductor pattern that includes a radiation conductor 121, a feed conductor 122, and a coupling conductor 123 formed on the substrate 110. Both the feed conductor 122 and the coupling conductor 123 are formed on a side surface 115 of the substrate 110. One end 122a of the feed conductor 122 is connected to a feed line, and other end 122b is connected to a ground pattern. A coupling portion 122b of the feed conductor 122 is substantially U-shaped, and the coupling conductor 123 is electromagnetically coupled to the coupling portion 122b of the feed conductor 122. Because the feed conductor 122 is gently curved, an electric filed concentration can hardly occur. The length of the feed conductor 122 can be increased, and thus it is possible to obtain a strong electromagnetic coupling with the coupling conductor 123.