An antenna, has a box conductive case having at least a single opening on an upper part, an internal conductor which is stored in the case, is disposed at a bottom, and is shaped like a letter “” which is one of Japanese katakana letters, a letter “u”, a letter “U”, a cramp, or an arc, and a feeding element which is stored in the conductive case and is connected to a feeding section disposed on the bottom of the conductive case, wherein the internal conductor other than parts disposed on the conductive case is not connected to the case.