1. A file searching method applied in an image processing device, the file searching method comprising: obtaining an original image file, wherein the original image file is segmented by time into a plurality of original image fragments, wherein each of the plurality of original image fragments comprises a plurality of key values indicating extra information other than captured images and stored with the captured images and respectively combined into the original image fragments of the original image file; receiving at least one searching condition; obtaining at least one key value among the plurality of key values, wherein the at least one key value corresponds 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.