An operation portion elevates or lowers imaging units of a robot in response to the user's operation of the operation portion, and when the robot is moved from a first work stand to a second work stand which have different heights, a control unit determines whether the difference between the height of the imaging units before the moving of the robot and the height of the second work stand is present in a predetermined range, and when the control unit determines that the difference is not present in the predetermined range, a display unit controls a display device to display information that instructs a user to change the height of the imaging units via the operation portion.