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 the COI area to identify a content characteristic in, wherein the content characteristic is related to a specific object; determining an implication attribute of the content characteristic, wherein the implication attribute includes an object category which the specific object belongs to; 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, wherein, during the step of selecting the context-of-interest (COI) area according to the touch input event, the touch input event comprise a plurality of touch points or a touch track, the related image searching method further comprises: selecting a first COI area and a second COI area together from the displayed image according to the touch points or the touch track of the touch input event; analyzing a first content characteristic in the first COI area and a second content characteristic in the second COI area; determining a first implication attribute of the first content characteristic and a second implication attribute of the second content characteristic; and searching the database according to a logical set formed by the first content characteristic, the first implication attribute, the second content characteristic and the second implication attribute, so as to identify at least one image file from the database with the same logical set.