1. A face recognition apparatus comprising: an image input unit to receive a face image of an identity verification subject; a face image generator to generate sub-images having different face sizes using the face image; a classification module to generate respective feature vectors of the sub-images, and to generate observation nodes based on the feature vectors; and a face recognizer to compare the observation nodes with stored reference nodes of sub-images of a registered person on a face size by face size basis to calculate respective similarity scores between the observation nodes and the reference nodes, generate respective state nodes based on the respective similarity scores, compare the observation nodes and the state nodes, and compare the state nodes to thereby perform face recognition.