1. An erasing apparatus, comprising: an erasing unit configured to perform an erasing process with respect to a plurality of sheets, each having images on both surfaces; a sheet scanner configured to scan both surfaces of each of the sheets and generate image data of each surface of said each sheet, before and after the erasing process; a sheet storage unit; and a controller configured to: determine, based on the image data, whether or not each surface of each of the sheets has become reusable as a result of the erasing process, and with respect to sheets of which only one surface is determined to be reusable, cause the reusable surfaces to face the same side in the sheet storage unit, and with respect to each sheet of which both surfaces are determined to be reusable, further cause a first surface determined to have been subjected to the erasing process a smaller number of times than a second surface to face upward in the sheet storage unit.