This study has focused on how university students understand the geometric representation of double integral. For this purpose, six participants have been asked six questions. Later, semi-structured interviews were conducted with the participants. In this study, the data obtained from questionnaire form and interviews were analyzed with open and axial coding. As a result of this research, it was observed that the concept images of university students were grouped into two categories as “area” and “volume”. It was determined that the participants acted with an intuitive approach without having to establish a relationship between the concept definition and the concept image, the ∬ in the symbol of the double integral caused the participants to think of it as a two-dimensional geometric structure and their image of the concept of the single integral was very active. The findings obtained in this research shows that there are problems in understanding the concept of the double integral, which is the first step of generalizing to multiple integrals, and that educator should produce solutions for this subject.