The recent portable terminal equipment including smart phone have various functions and have been required high performance and communication quality. And the built-in antenna for portable terminal apparatus have been required miniaturization and low posture. In this study, we put emphasis on excitation of handset antenna. And we use the characteristic mode analysis (CMA) for small handset antenna design. This analysis method has been employed to exploit the resonant mode of the handset antenna and ground plane. This paper presents the principle of resonant mode of small handset antenna with the multi-band by using the CMA.