1. An estimation apparatus for estimating a position and orientation of an object, comprising: a capturing unit adapted to capture an object targeted for position and orientation estimation, and generate a range image representing distance information from the capturing unit to the target object; a general estimation unit adapted to analyze the range image and estimate a general position and orientation of the target object; a plurality of identification units each adapted to estimate a detailed position and orientation of an object within a predetermined position and orientation range; a determination unit adapted to determine a priority order of the plurality of identification units, based on the general position and orientation estimated by the general estimation unit; and a detailed estimation unit adapted to estimate a detailed position and orientation of the target object, using the plurality of identification units in the priority order determined by the determination unit.