1. A method for detecting a face, comprising: detecting a circle from an input image by using a Hough transform; forming image fragments of the same size in a region of the detected circle; generating input vectors for each of the image fragments by using each classifier of a cascade that includes homogeneous classifiers; and when an input vector generated by the image fragments is classified into a face type by the classifier of the cascade, determining that a face is detected from the input image.