1. An additional information attaching device comprising: an image input section for inputting an image; an attribution acquisition section for acquiring attribution elements of said input image as image attribution elements; a candidate additional information storage section for storing pieces of candidate additional information, reference attribution elements, which are preliminarily prepared for each piece of said candidate additional information, representing attribution relevant to the contents of said candidate additional information, and first compatibility degrees of said reference attribution elements; a compatibility evaluation section for evaluating second compatibility degree between said input image and said candidate additional information based on said first compatibility degrees of said reference attribution elements correlated with said image attribution elements acquired from said input image; an additional information selecting section for selecting additional information from among said pieces of candidate additional information based on said second compatibility degree evaluated in said compatibility evaluation section; and an attaching section for attaching a tag having said additional information selected in said additional information selecting section to said input image.