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: a view-point image generation unit configured to generate a plurality of view-point images obtained by observing the measurement object from a plurality of different view-points using the three-dimensional geometric model; an edge detection unit configured to detect edges of the measurement object from the plurality of view-point images as second edges; a reliability calculation unit configured to associate the second edges with the first edges, respectively, and calculate respective reliabilities of the first edges based on the association result; a weighting unit configured to weight each of the first edges based on the respective reliabilities of the first edges calculated by said reliability calculation unit; and a position/orientation calculation unit configured to associate third edges detected from a captured image obtained by capturing an image of the measurement object with the first edges weighted by said weighting unit, and calculate a position and an orientation of the measurement object based on the association result.