1. A three-dimensional measurement apparatus, which measures a position and an orientation of a measurement object using a three-dimensional geometric model that defines a shape of the measurement object using a plurality of first edges, said apparatus comprising: an edge detection unit configured to detect, as second edges, edges corresponding to the plurality of first edges from the plurality of view-point images obtained by rendering the three-dimensional geometric model of a measurement object at a plurality of different view-points; a counting unit configured to count a number of times the second edges are detected from the plurality of view-point images; a reliability assigning unit configured to assign reliabilities of the plurality of first edges based on the number of times the second edges are detected from the plurality of view-point images; an association unit configured to associate third edges detected from a captured image with the first edges; and a position/orientation calculation unit configured to calculate a position and an orientation of the measurement object based on the association result and the assigned reliabilities of the first edges.