A scanner including an automatic document feeder includes a communication interface unit to perform a communication with an external printer; a scan operation performing unit to perform a scan operation; an automatic feeding unit to automatically feed scan-target documents to the scan operation performing unit; and a controller to control the scan operation and a scan speed, wherein when the communication interface unit receives a request speed for a scan operation from the external printer, the controller adjusts a feeding interval between the scan-target documents that are fed from the automatic feeding unit, so that the scan operation is performed at the received request speed.