This paper introduces a novel robot which is able to climb hanger cables of long span suspension bridges. The robot has been developed for inspection purpose, and it can help us remotely inspect the state of cables by using cameras and Non-Destructive Testing (NDT) devices. The robot consists of two traction modules, two sub modules, and an adhesion mechanism. The unique design of the traction module ensures the stable movement of the robot on the twisted surface of the hanger cable. In this paper, we describe the structure and environmental situation of hanger cables and the mechanisms of the robot. Also, the results of experiments in the indoor and outdoor environments are included.