This study visualizes the results of sandplay therapy in a time series using a newly developed 3D visualization technique, aiming to interpret the outcomes using quantitative data alongside conventional expert-based interpretations. The technique generates 3D sandplay data using point cloud data and visualizes the undulations of the sand surface through a luminance gradient effect based on the translucent visualization method [JOVI]. A key feature of this technique is its ability to segment information at the part-level of sand and figurines, enabling dynamic interpretations over time. In this study, the quantitative interpretation focused on changes in the height variance of sand and figurines. Subtle changes in variance, difficult to detect from photographs or images alone, were observed over time, allowing tracking of the client’s psychological changes. Moreover, the study revealed that such quantitative indicators can substantiate and enhance expert interpretations.