Recently, the Fintech industry is growing rapidly, and mobile payment service plays a key role in this growth. The purpose of this study is to investigate factors affecting initial acceptance of mobile payment service using Technology Acceptance Model. In the research model, service-related factors such as economic efficiency and security, user-related factors such as user innovativeness and social factors such as social influence were adopted as external variables, and acceptance intention was introduced as dependent variable. Perceived usefulness and perceived ease of use were selected as mediating variables. The collected data were analyzed using SPSS Statistics v22 and Smart PLS 2.0. The results of the study are as follows. First, service-related factors such as economic efficiency and security did not affect the user acceptance intention. Second, individual innovativeness and social influence have significant effects on perceived usefulness and perceived ease of use respectively. And the perceived usefulness and perceived ease of use, which are mediators, have a significant influence on the acceptance intention of mobile payment service. The results of this study will serve as a useful guide for Fintech industries.