1. An information processing apparatus which creates a classifier for classifying an attribute of a pattern image using a plurality of nodes consisting of a tree structure, comprising: an input unit configured to input a plurality of learning pattern images to each of the plurality of nodes, each of the plurality of learning pattern images including a target object; a selection unit configured to select, from each of the plurality of learning pattern images inputted to the node, at least one point; a determination unit configured to determine, for each of the plurality of learning pattern images inputted to the node, whether the selected point belongs to a region of the target object in the learning pattern image; a distribution unit configured to distribute and input, to a lower node of each node, a learning pattern image for which said determination unit has determined that the selected point belongs to the region; a deletion unit configured to delete a learning pattern image for which said determination unit has determined that the selected point does not belong to the region; and a storage unit configured to store an attribute of the learning pattern image input to a terminal node of the plurality of nodes in association with the node, wherein said selection unit selects, from each of the plurality of learning pattern images inputted to the node, a plurality of points, said determination unit determines, for each of the plurality of learning pattern images inputted to the node, whether a ratio of the selected plurality of points belonging to the region of the target object in the learning pattern image is larger than a threshold, said distribution unit distributes and inputs, to a lower node of each node, a learning pattern image for which said determination unit has determined that the ratio of the selected plurality of points belonging to the region of the target object in the learning pattern image is larger than the threshold, and said deletion unit deletes a learning pattern image for which said determination unit has determined that the ratio of the selected plurality of points belonging to the region of the target object in the learning pattern image is not larger than the threshold.