1. An image processing device comprising: a partial image extracting section extracting a partial image from an inputted image; a type distinguishing section distinguishing a type of the partial image; a plurality of partial image databases provided respectively for each of the types, and storing registered partial images and photographing time periods of the registered partial images in association with one another; a characteristic information generating section generating characteristic information of the partial image and characteristic information of the registered partial images; a degree of similarity computing section computing, on the basis of both characteristic information, degrees of similarity between the partial image and the registered partial images which are stored in the partial image database which corresponds to the type of the partial image; a photographing time period specifying section specifying a photographing time period of the inputted image, on the basis of results of computation by the degree of similarity computing section; and an outputting section outputting the photographing time period which is specified.