This research was conducted to find mathematical elements (ethnomathematics) in the Sumur Gumuling Tamansari building. The research method used in this study is a qualitative method with an ethnographic approach. The data used are data obtained from observations, documentation, and interviews. Observation and documentation are used to identify ethnomathematics in the Sumur Gumuling Tamansari building. While documentation and interviews with the triangulation method to find out more deeply the cultural values that exist in the Sumur Gumuling Tamansari building. The results of this study are there are mathematical elements (ethnomathematics) in the Sumur Gumuling Tamansari building, namely the concept of a rectangle, pentagon, rhombus, triangle, circle, and the combined concept of a rectangular flat structure with a half-circle. In this case, it can be said that mathematics enters a ll aspects of life including cultural buildings.