The present invention relates to a voice recognition apparatus capable of easily registering a word which has not been registered. The registering of an unregistered word into a dictionary can be easily performed without causing a significant increase in the size of the dictionary. The clustering unit detects a cluster (detected cluster) to which a new unregistered word is to be added as a new member, from existing clusters obtained by clustering unregistered words. The unregistered word is added as a new member to the detected cluster, and the cluster is divided depending on the members of the cluster such that unregistered words which are acoustically similar to each other belong to the same cluster. The maintenance unit updates the word dictionary on the basis of the result of the clustering. The present invention may be applied to a robot including a voice recognition apparatus.