In this study, multi-band antenna using the intra coupling effect is proposed. From the experimental and simulated results, it was confirmed that the proposed antenna has two resonant frequencies. In this paper, the mechanism achieving multi-band characteristics is investigated by changing the coupling effect. As a result, the low resonant frequency is dependent on the coupling effect. The high resonant frequency is dependent on the size of antenna. We confirm the relationship between the coupling effect and the antenna characteristics.