It is afraid that space debris damage outer wall of International Space Station (ISS). Inspecting the wall is very important because even small crack has potential to bring critical problems. However, the inspection is dangerous and time-consuming task for astronauts. In this paper, a space robot system for inspecting outer wall of ISS is proposed. The inspection robot walks on the handrails attached on the outer wall of ISS, and inspects the wall with the camera. A feasibility study of the inspection task by the robot is carried out with a numerical model and dynamics simulation.