In this paper, we present a virtual reality (VR) simulator for four-arm disaster response robot OCTOPUS, which has high capable of both mobility and workability. OCTOPUS has 22 degrees of freedom (DOF), so it is quite difficult to operate OCTOPUS. We thus developed a VR simulator for training operation, revealing operations and systems to be improved, and developing operator support systems. VR simulator can conduct experimental environments at lower cost and higher efficiency. Our VR simulator consisted of VR environment and human-machine interface such as operation-input and video- and sound-output, based on robot operation system (ROS) and Gazebo. Four tasks such as rough terrain translation, step climbing, obstacle stepping over, and object transport were conducted to evaluate OCTOPUS itself and our VR simulator. The results indicate that operators could complete all the tasks and reveal key operations for stable task execution.