Abstract: An antenna is provided which can reconcile a low antenna resonance frequency and broadband frequency characteristics, while attaining stable impedance characteristics and enhanced designing flexibility. A conductive plate 12 is coupled to a conductive base plate 11 via a metal lead 14. A voltage is applied to the conductive plate 12 from a supply point 15 via a metal lead 13. A conductive wall 16 is electrically coupled to the conductive plate 12 at one end thereof. An electromagnetic field coupling adjustment plate 17 is electrically coupled to the other end of the conductive wall 16. The electromagnetic field coupling adjustment plate 17 is disposed so as to leave a predetermined interspace between itself and the conductive base plate 11, thereby creating a capacitor in conjunction with the conductive base plate 11.