An image is displayed without impairing visibility, even in the case of a screen having a limited size. A display setting unit includes a target image display unit that displays an image of a workpiece on an LCD, an image selection unit that, in accordance with a selection operation, selects all or part of the image of the workpiece displayed on the LCD, a menu display unit that displays a menu image so as to be overlapped with the image of the workpiece in a translucent state, the menu image being made up of a plurality of parts that are partial images for displaying information or receiving an input operation, and a display switching unit that, in accordance with a switching instruction given via the operation unit, switches the size of the area occupied by the menu image on the LCD.