An apparatus for discrimination includes a memory, an alignment unit configured to align nodes of a decision tree in the memory, wherein a node in which depth from a root node is not greater than a threshold is aligned in accordance with a breadth of first order, and a node in which depth from a root node is greater than a threshold is aligned in accordance with a depth of first order, and a discrimination unit, receiving an inputted data, configured to discriminate a class of the inputted data using the nodes aligned in the memory.