An information management apparatus includes a characteristic-amount management unit managing a characteristic amount; a characteristic-amount association unit maintaining an association with a similar characteristic amount for each of the characteristic amounts; a space index management unit managing a space index for the characteristic amounts managed by the characteristic-amount management unit; a partial space determination unit determining a partial space in the space index to which a first characteristic amount belongs in accordance with a request for retrieving a characteristic amount similar to the first characteristic amount; and a similarity determination unit calculating similarity between the first characteristic amount and a second characteristic amount and between the first characteristic amount and a third characteristic amount associated with the second characteristic amount by the characteristic-amount association unit, and determines which characteristic amounts are similar to the first characteristic amount by comparing the calculated similarity and a predetermined threshold.