Patent ID: 8687231

Claim:
A decoloring device comprising: a decoloring unit that decolors an image formed with a decolorable coloring agent on a sheet; a first sheet conveying unit that conveys the sheet to the decoloring unit; a pre-decoloring reading unit that reads the image on the sheet conveyed by the first sheet conveying unit before the decoloring; a type determining unit that determines a type of content on the sheet conveyed to the decoloring unit, based on the image read by the pre-decoloring reading unit; a second sheet conveying unit that conveys the sheet from the decoloring unit; a post-decoloring reading unit that reads a remaining image on the sheet conveyed by the second sheet conveying unit after the decoloring; a determination criterion setting unit that sets at least one determination criterion for determining whether or not the decoloring by the decoloring unit is successful based on the determined type of content; and a decoloring success or failure determining unit that determines whether or not the decoloring of the image on the sheet by the decoloring unit is successful based on the remaining image read by the post-decoloring reading unit and based on the determination criterion set by the determination criterion setting unit.