Decolorizing device and method for controlling decolorizing device

A decolorizing device comprising:

• a first stacker to stack sheets having images thereon to be decolorized;
• a second stacker arranged adjacent to the first stacker, wherein sheets stacked on the first stacker are kept waiting on the second stacker in order to decolorize the images;
• an image decolorizing unit to decolorize the images on the sheets;
• a sheet feed unit to convey a sheet from the second stacker to the image decolorizing unit;
• a first judging unit to determine whether the sheet conveyed by the sheet feed unit is reusable or not;
• a first nonreusable sheet stacker to receive a sheet that is judged by the first judging unit to be nonreusable;
• a second judging unit to determine whether a sheet from which the image is decolorized by the image decolorizing unit is reusable or not;
• and
• a second nonreusable sheet stacker to receive a sheet that is determined by the second judging unit to be nonreusable.