The key roles of dam foundation rock mass are to provide sufficient strength to support dam embankment, and to resist to leakage of water. When considering resistance to leakage of water, it is important to understand the fluid flow within the rock mass. For example, in fractured rock mass, fluid tends to flow through permeable fractures. Therefore, in such case, understanding fracture properties (size, intensity, and orientation) of dam foundation rock mass is critical in support of dam foundation design. Fracture data are collected through geological surveys including core logging and surface mapping. Although surface mapping such as window mapping allows collection of two-dimensional (2-D) data of fractures, surface mapping typically requires field geologists to manually record geological information and tends to be time-consuming. In recent decade, with the advancements in remote sensing techniques and computer efficiency, there are new technologies to acquire digital field data remotely at shorter time. One example is the application of UAV (Unmanned Aerial Vehicle) based photogrammetry combined with SfM (Structure from Motion) techniques in acquisition of fracture data. Although this technique has been applied to various rock engineering applications, the application to flat rock surface such as dam foundation rock mass has not been examined. This paper studies the application of UAV-based photogrammetry to extract fracture planes from flat rock surface using a case study of dam foundation rock mass in Japan and examines the results by comparing fracture properties. The comparison showed strong agreement between fracture orientations and distributions obtained through UAV-based photogrammetry and window mapping, which implied applicability of the method to dam foundation rock mass.