1. An image processing device comprising: an attribute storage unit that stores a photographic attribute for each of a plurality of events, each photographic attribute indicating a photographic condition predicted to be met with respect to an image photographed in the corresponding event; an object information storage unit that stores, for each event, an object predicted to appear in an image photographed in the corresponding event; an extracting unit that extracts from a collection of photographed images a photographic attribute that is common among a predetermined number of photographed images in the collection, based on pieces of photography-related information of the respective photographed images; a specifying unit that specifies an object stored, in the object information storage unit, for an event corresponding to the extracted photographic attribute; and an associating unit that conducts a process on the collection of photographed images to associate each photographed image containing the specified object with the object.