To provide an image input device capable of obtaining the data of both black reference and white reference without forcing complicated operations on a user even in a device incapable of easily turning a light source to an OFF state by rotating a reference sheet in linkage with a paper feed roller and reducing the influence of dust stuck to the reference sheet or the like by using the average value of reference data for plural lines, and to provide a reference data obtaining method and a storage medium.

This device is provided with the paper feed roller 5 driven by a motor 3 for feeding an original 1, reference sheet holding shafts 7 and 8 for holding the reference sheet 9 and circulating the reference sheet 9 in a route including the light receiving surface of a sensor unit 12 and the cleaner part of reference sheet pressing devices 15 and 16 driven by the motor 3 and a CPU for controlling the drive of the motor 3 so as to circulate the reference sheet 9 in linkage with the paper feed roller 5.