According to an embodiment, a pattern classifier device includes a decision unit, an execution unit, a calculator, and a determination unit. The decision unit is configured to decide a subclass to which the input pattern is to belong, based on attribute information of the input pattern. The execution unit is configured to determine whether the input pattern belongs to a class that is divided into subclasses, using a weak classifier allocated to the decided subclass, and output a result of the determination and a reliability of the weak classifier. The calculator is configured to calculate an integrated value obtained by integrating an evaluation value based on the determination result and the reliability. The determination unit is configured to repeat the determination processing when a termination condition of the determination processing is not satisfied, and terminate the determination processing and output the integrated value when the termination condition, has been satisfied.