1. A related image searching method, suitable for searching a database storing a plurality of image files, the related image searching method comprising: selecting a context-of-interest (COI) area from a displayed image according to a touch input event; analyzing a content characteristic in the COI area; determining an implication attribute of the content characteristic; and searching the database according to the content characteristic and the implication attribute, so as to identify at least one image file from the database with the same content characteristic or the same implication attribute.