The main Objectives of this paper are as follows. First, we investigated effects of Smart Phone quality on the usefulness and ease of use of Smart Phone. Then, we investigated effects of the usefulness and ease of use of Smart Phone on the intention of use. Our research model is based on TAM(Technology Acceptance Model). To accomplish the purpose of this paper effectively and efficiently, a survey was conducted based on the usage of Smart Phone. Then we conducted regression analyses on the collected data and found following results. First, Smart Phone quality have a significant effect on the usefulness and ease of use of Smart Phone. Second, the usefulness and ease of use of Smart Phone have significant effects on the intention of use. Third, Smart Phone users are more satisfied with the system quality than cellular phone users. And the continuous use intention of Smart-Phone users is higher than that of cellular phone users.