1. An information processing apparatus which creates a classifier for classifying an attribute of a pattern using a plurality of nodes consisting of a tree structure, comprising: a creation unit configured to create, for each of the plurality of nodes, a query to be executed for a learning pattern input to the node; an input unit configured to input a plurality of learning patterns to a root node of the plurality of nodes; an execution unit configured to execute, for the learning pattern input to each node, the query created for the node; a determination unit configured to determine whether the query has been effectively executed for the individual learning pattern input to each node; a distribution unit configured to distribute and input, to a lower node of each node, an individual learning pattern for which said determination unit has determined that the query was effectively executed in the node; a deletion unit configured to delete a learning pattern for which said determination unit has determined that the query was not effectively executed in each node; and a storage unit configured to store an attribute of the learning pattern input to a terminal node of the plurality of nodes in association with the node.