1. A position and orientation measurement apparatus comprising: an acquisition unit configured to acquire, from an image including a target object, at least one coarse position and orientation of the target object; a generation unit configured to generate, based on the acquired coarse position and orientation, at least one candidate position and orientation which is different from the coarse position and orientation as an initial position and orientation used for deriving a position and orientation of the target object; and a deriving unit configured to derive the position and orientation of the target object in the image by associating model information of the target object with the target object in the image based on the candidate position and orientation generated as the initial position and orientation.