According to an embodiment, an arithmetic operation apparatus for a neural network includes an input layer calculator, a correction unit calculator, a hidden layer calculator, and an output layer calculator. The input layer calculator is configured to convert an input pattern into features as outputs of an input layer. The correction unit calculator is configured to perform calculation on N unit groups corresponding respectively to N classes of the input pattern and including correction units that each multiply a value based on inputs by a weight determined for the corresponding class. The hidden layer calculator is configured to perform calculation in a hidden layer based on the outputs of the input layer, another hidden layer, or the correction unit calculator. The output layer calculator is configured to perform calculation in an output layer based on the calculation for the hidden layer or the outputs of the correction unit calculator.