A scan-mode changeable image duplicating apparatus having operational parameters and modes of operation and operative to duplicate a document in accordance with selected ones of the operational parameters and modes of operation, including a recirculating document feeder unit having a document storage tray and a passageway through which a document is to be withdrawn from the tray and returned to the tray by way of an exposure position in which the document is to be scanned, a scanning unit for scanning a document in the exposure position, the scanning unit being movable back and forth with respect to the exposure position, a control system for controlling the document feeder unit and the scanning unit to operate either in a scanner-moved scanning mode in which the scanning unit is driven to move with respect to the exposure position to scan a document fixedly held in the exposure position and a document-moved scanning mode in which the scanning unit is fixed with respect to the exposure position and scans a document being moved with respect to the exposure position, and keys for entering desired ones of the operational parameters and the modes of operation for automatically selecting the scanning mode in which the control system is to control the document feeder unit and the scanning unit.