1. An image processing device comprising: a processor; and a non-transitory memory having stored thereon executable instructions which, when executed, cause the processor to perform at least the following: storing, in an attribute storage unit, 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; storing, in an object information storage unit, for each event, an object predicted to appear in an image photographed in the corresponding event; extracting 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; specifying an object stored, in the object information storage unit, for an event corresponding to the extracted photographic attribute; and conducting an associating process on the collection of photographed images to associate each photographed image containing the specified object with the object.