A method of controlling a foldable display device according to one embodiment of the present specification can include the steps of displaying a first image in a first area, a second image in a second area, and a third image in a third area in a mode that a foldable display device is not folded, wherein the first area is positioned at the center of the foldable display device, the second area is positioned at the left of the first area, and the third area is positioned at the right of the first area, detecting that the second area or the third area of the foldable display device is folded, if the second area is folded, assigning the first image to a first image layer of the first area and assigning the second image of the folded second area to a second image layer of the first area.