1. An apparatus for generating facial animation, the apparatus comprising: a pre-processing unit for selecting an image frame having a facial region that is most similar to a facial region of one of a plurality of key models of facial characters, from a sequence of image frames, each image frame being divided into a plurality of facial regions; a facial animation generation unit for determining a blending weight for each selected facial region of the key models using the selected facial region and for synthesizing facial character shapes on a facial region-by-facial region basis using the determined blending weight for each facial region of each of the key models; and a display device for displaying facial animation, wherein the pre-processing unit compares directions of respective two-dimensional (2D) displacement vectors of vertices included in each key model with directions of respective optical flow vectors of pixels included in each image frame and calculates a similarity between the directions, wherein the 2D displacement vectors are determined based on vertices included in one of the key models, and the optical flow vectors of the pixels are generated by calculating optical flows of the pixels based on pixels included in one of the image frames.