A robot simulator includes a storage device that stores model information related to the robot and an obstacle in the vicinity of the robot, and an acquisition device that obtains first input information defining a start position and an end position of operation of the robot. A processing device generates a path for moving the distal end portion of the robot from the start position to the end position while avoiding collisions between the robot and the obstacle based on the first input information and the model information. The processing device also generates image data including an illustration of the obstacle and an index indicating a via-point of the path.