The purpose of this study was to design and develop an educational game which facilitates building adolescents' knowledge and attitudes in financial principles of a daily life. To achieve this purpose, the authors designed a learner-centered big game for financial education by applying an experience-based triple-diamond instructional design model using service design processes and tools. The big game prototype for financial education implemented in a virtual space utilizing an iPad toolkit. A virtual Lost City and the physical space of Korea's financial center of Yeouido tightly integrated into the big game. As a result of the prototype evaluation sessions with 18 high school sophomores, the authors demonstrated how a big game could be effective in school settings. The learners said they enjoyed gaining the financial principles by communicating with other learners. This study also suggested a great potential for using a service design approach in developing the big game.