An erasing device to erase an image displayed on a display apparatus, the erasing device including: a housing; a generator to generate an electromagnetic field so that the electromagnetic field is emitted from each of a plurality of portions of a tip of the housing; and a controller to control the generator to generate the electromagnetic field when the tip touches a surface of the display apparatus so that the display apparatus detecting the electromagnetic field erases an image within a preset image deletion region with a predetermined area based on a position on the surface touched by the tip, wherein the generator adjusts output of the electromagnetic field from each portion of the tip based on whether each portion of the tip touches the surface so that the display apparatus adjusts the area of the image deletion region based on the portion of the tip touched by the surface.