A method of performing a class incremental learning in a neural network apparatus, the method including training an autoencoder using first input embeddings with respect to a first class group, calculating a contribution value of each of parameters of the autoencoder and calculating a representative value with respect to each of at least one first class included in the first class group in the training of the autoencoder, retraining the autoencoder using second input embeddings with respect to a second class group, and updating the contribution value of the each of the parameters and calculating a representative value with respect to each of at least one second class included in the second class group in the retraining the autoencoder.