This paper presents a antenna composed of metal case with a slot and inner folded dipole antenna. The proposed antenna structure simultaneously achieve the miniaturization of the metal case and the wide bandwidth. The impedance bandwidth of 15.9 % with the size of 0.35λ 0 ×0.35λ 0 ×0.03λ 0 (λ 0 is the wavelength of low frequency) can be realized by the proposed structure. The proposed structure is validated by the comparison of the simulation and measurement result.