Patent ID: 8821096

Claim:
A decoloring device comprising: a sheet conveying unit that includes a conveying path configured to convey a sheet; a decoloring unit positioned in the conveying path of the sheet conveying unit and configured to decolor an image formed with a decolorable coloring agent on a sheet a first sheet feed unit configured to feed the sheet to the sheet conveying unit; a thickness detecting unit positioned in the conveying path of the sheet conveying unit downstream relative to the first sheet feed unit and upstream relative to the decoloring unit, the thickness detecting unit configured to detect a thickness of the sheet conveyed by the sheet conveying unit from the first sheet feed unit toward the decoloring unit; a decolorability determining unit configured to detect whether or not the image on the sheet is decolorable by the decoloring unit based on a detection result in the thickness detecting unit; a second sheet feed unit positioned in the conveying path of the sheet conveying unit downstream relative to the thickness detecting unit and upstream relative to the decoloring unit and configured to feed a sheet to the sheet conveying unit, the second sheet feed unit feeding sheets to the decoloring unit without the sheets passing through the thickness detecting unit; a pre-decoloring reading unit configured to read the image on the sheet conveyed by the sheet conveying unit from the first sheet feed unit to the decoloring unit; and a reusability determining unit configured to determine whether or not the sheet which is subject to image reading is reusable based on a reading result in the pre-decoloring reading unit.