The operation device according to the present invention includes a touch panel configured to enable selection of a predetermined key contained in a predetermined screen, a function screen display reception unit for displaying a screen including a screen area and a retreat area being an area that is different from the screen area, an operation unit, a screen switching reception unit for displaying an icon key corresponding to the function of the second function screen on the touch panel in a selectable configuration at a predetermined position of the retreat area, a reduced screen display reception unit that displays a first reduced screen key for reducing the first function screen on the touch panel in a selectable configuration in the retreat area, and a function screen switching unit for switching the display of the first function screen in the screen area to the display of the second function screen.