1. A pattern identification unit generation method of generating a pattern identification unit in which a weak discriminator array obtained by cascade-connecting a plurality of weak discriminators branches, and weak discriminator arrays are connected to respective arms after branching, the method comprising: an evaluation step of evaluating based on a processing result obtained by inputting a set of evaluation data to the weak discriminator array whether or not a weak discriminator array after branching reaches the number of stages to be connected; a determination step of determining, based on an evaluation result in the evaluation step, the number of stages of weak discriminators to be connected without branching as the weak discriminator array after branching.