A decoloring system comprising a decoloring device which decolors an image on a sheet and a management device, the decoloring device cooperating with and communicating with the management device and comprising: a sheet conveying path which conveys the sheet to each unit inside the device; a sheet feeding unit including a sheet-stacking part which feeds the sheet on which the image is formed with a decolorable colorant to the sheet conveying path from the sheet-stacking part; a scanning unit which is provided downstream of the sheet feeding unit on the sheet conveying path and scans the image on the sheet; a decoloring unit which is provided downstream of the scanning unit on the sheet conveying path and decolors the image on the sheet; a communication unit which transmits image data of the sheet which precedes a following sheet scanned by the scanning unit to the management device and receives from the management device conveyance destination indication data which is produced by the management device based on the image data, the conveyance destination indication data comprising a determination result by the management device on whether or not the image data of the sheet includes prohibited data for which decoloring is prohibited, and indicating the conveyance destination of the sheet; and a control unit which conveys the sheet, to a predetermined conveyance destination based on the conveyance destination indication data, characterized in that the communication unit is configured to further receive from the management device reception time indication data indicating time taken for the decoloring device to receive the conveyance destination indication data from the management device; and in that the control unit is configured to feed sheets at a timing at which the leading end of a following sheet does not run into the tail end of the sheet even if the sheet is held between the scanning unit and the decoloring unit until the conveyance destination indication data is received based on the reception time indication data. a sheet conveying path which conveys the sheet to each unit inside the device; a sheet feeding unit including a sheet-stacking part which feeds the sheet on which the image is formed with a decolorable colorant to the sheet conveying path from the sheet-stacking part; a scanning unit which is provided downstream of the sheet feeding unit on the sheet conveying path and scans the image on the sheet; a decoloring unit which is provided downstream of the scanning unit on the sheet conveying path and decolors the image on the sheet; a communication unit which transmits image data of the sheet which precedes a following sheet scanned by the scanning unit to the management device and receives from the management device conveyance destination indication data which is produced by the management device based on the image data, the conveyance destination indication data comprising a determination result by the management device on whether or not the image data of the sheet includes prohibited data for which decoloring is prohibited, and indicating the conveyance destination of the sheet; and a control unit which conveys the sheet, to a predetermined conveyance destination based on the conveyance destination indication data, characterized in that the communication unit is configured to further receive from the management device reception time indication data indicating time taken for the decoloring device to receive the conveyance destination indication data from the management device; and in that the control unit is configured to feed sheets at a timing at which the leading end of a following sheet does not run into the tail end of the sheet even if the sheet is held between the scanning unit and the decoloring unit until the conveyance destination indication data is received based on the reception time indication data.