A displaying method of a robot simulator for intuitively recognizing the working direction of a tool is provided. A displaying method on a robot simulator includes displaying a real image of a robot to mount a tool at an end effector of a robot arm, displaying a tool coordinate system indicating an operating direction of the tool at the end effector of the robot arm which is displayed in the displaying of the real image of the robot, displaying a virtual reality (VR) image having a three-dimension image at the end effector of the robot arm which is displayed in the displaying of the real image of the robot.