Rotaxane molecules have attracted considerable interest because of their good performance in both molecular electronic devices and nanoscale data-storage media. Low-temperature scanning tunneling microscopy is used to investigate the structure and conductance of single H2 rotaxane molecules on a buffer-layered Au(111) substrate at 77 K. It is demonstrated that the conductance switching in rotaxane-based, solid-state devices is an inherent property of the rotaxane molecules. These results provide evidence that the conductance switching might arise from the movement of the cyclobis(paraquat-p-phenylene) ring along the rod section of the dumbbell-shaped backbone of the rotaxane molecule.