According to one embodiment, an decoloring apparatus includes: an decoloring processing unit configured to apply decoloring processing decoloring a color of an decolorable colorant; a sheet conveying unit configured to convey the sheet and cause the sheet to pass through the decoloring processing unit; an image reading unit arranged further on an upstream side than the decoloring processing unit in a sheet conveying direction by the sheet conveying unit and configured to read the image formed on the sheet conveyed by the sheet conveying unit; a thickness sensor arranged further on the upstream side than the decoloring processing unit in the sheet conveying direction by the sheet conveying unit and configured to detect thickness of the sheet conveyed by the sheet conveying unit; an decolorability determining unit configured to determine, on the basis of a detection result in at least one of the image reading unit and the thickness sensor, executability of the decoloring processing in the decoloring processing unit of the sheet set as a detection target; a storing unit configured to store information indicating a number of sheets determined as decoloring processing unexecutable by the decolorability determining unit; and a display control unit configured to cause, when the apparatus is started, a display to screen-display the information stored in the storing unit indicating the number of sheets determined as decoloring processing unexecutable by the decolorability determining unit.