1. A file searching method, for searching an original image file in an image processing device, wherein the original image file comprises a plurality of original image fragments and each of the plurality of original image fragments comprises a plurality of key values, the file searching method comprising: receiving at least one searching condition; obtaining at least one corresponding key value among the plurality of key values according to the at least one searching condition; and searching at least one searching image fragment meeting the at least one searching condition from the plurality of image fragments.