Observation of tunnel excavation faces is one of the crucial tasks for ensuring safe construction. Photographs of the faces sometimes complement geological engineers’ visual investigation; however, they are insufficient for a comprehensive geological assessment. Instead of the conventional methods, we have developed a method for observing tunnel faces in virtual reality (VR), using visualization of 3D point cloud data with a customized software. Two types of manual strike and dip orientation measurement functions for discontinuities have been implemented in the software. To validate its effectiveness, we applied the method to tunnel sections where weathered and altered andesite and talus deposits were distributed. The method identified unconformities at the bottom of the talus, which were unclear from photographs alone. Moreover, the measured strike and dip data quantified the geological structure of the unconformity. From these results, we conclude that the VR observation is more effective for detailed geological evaluation than the conventional 2D photographic methods.