A learning apparatus acquires a plurality of training samples containing a plurality of attributes and known classes, gives the plurality of training samples to a route node of a decision tree to be learned as an identifier, generates a plurality of child nodes from a parent node of the decision tree, allocates the training samples whose attribute corresponding to a branch condition for classification is not a deficit values at the parent node of the decision tree out of the plurality of training samples, to any of the plurality of child nodes according to the branch condition, gives the training samples whose attribute is the deficit value, to any one of the plurality of child nodes, and executes the generation of the child nodes and the allocating of the training samples until a termination condition is satisfied.