An image scanning system comprises: an image-capturing device that captures an image of a scan original and outputs image signals; an image processing circuit that executes image processing on the image signals; an image signal output device that outputs the image signals having undergone the image processing; a calculation device that calculates an estimated length of required time to complete image signal output after a scan instruction with regard to the scan original is issued; and a calculation result output device that outputs calculation results obtained at the calculation device.