According to an embodiment, a decolorizing section is placed on a downstream side of a first reading section in a sheet transferring direction. A second reading section is placed on a downstream side of the decolorizing section in the sheet transferring direction. A controller is configured to determine if the decolorizing process is necessary or not on a first side of a sheet based on first image data of the first side read by the first reading section, to read the first side of the sheet having been subjected to the decolorizing process at the decolorizing section by the second reading section if it is determined that the decolorizing process is necessary, and to avoid reading of the first side of the sheet passed through the decolorizing section by the second reading section if it is determined that the decolorizing process is unnecessary.