Curriculum integrations in Korea tend to take different integration approaches, but mostly they make students interests and activities the main driver of curriculum development. However, given the recent emphasis on the in-depth understanding of knowledge and its application and use in education, the design of the integrated curriculum should be changed. Therefore, this study seeks to explore a case of curriculum design that enables students to think deeply while taking a transdisciplinary approach. For this purpose, we analyzed the PYP of IB, which uses big ideas in transdisciplinary integration, to show why and how big idea-oriented integration can be an alternative to activity-oriented integration. Then we provided implications for the development of a big idea-based integrated curriculum.