A robot simulation device is provided. It includes a virtual robot working environment in which a virtual robot has a task of transferring a virtual object from a start point to a goal point, the simulation device determining the path of travel. A task simulation is executed in response to the virtual robot working environment and the path of travel. The task simulation determines a robot activity region where the virtual robot can operate and an interference region where the virtual robot encounters obstacles. Thereafter the device creates a desired executed simulation in which the virtual robot can operate without encountering obstacles.