In object recognition using image information, countermeasures are taken for reducing erroneous judgment caused when the similarity between a visual feature of an object image and a visual feature of dictionary data of another object becomes high in association with a temporal change. In a dictionary update method for a computer for updating dictionary data in which a visual feature of an object which a user desires to recognize is registered: when there are a plurality of data pieces having a visual feature similar to the inputted inquiry image, visual features of a plurality of objects are concluded as being similar and hence the pair of objects are accumulated into a similar object accumulation section; and when the objects accumulated in the similar object accumulation section have reached a condition set forth in advance, data having the visual features of the objects having reached the condition is concluded as requiring update and hence update is recommended to a user having registered the object.