A method and apparatus for using a neural network to categorize patterns from pattern feature data derived from the patterns. The average of all the learning data of the neural network is subtracted from the pattern feature data, and the result is input to the input layer of the neural network. The neural network outputs a value for each category and the pattern is categorized based on these values. The neural network includes an intermediate layer whose bias is set to zero and which includes a sigmoid transfer function which is symmetric with respect to the origin.