1. A face detection method, comprising: (a) generating divided input image portions by dividing an input image into a predetermined number of regions, the input image including a frame from a plurality of frames sequentially received during a predetermined time period; (b) resizing the respective divided input image portions of a first frame and performing a face detection operation on the divided and resized input image portions, when in a full detection mode operation; (c) when a face is detected in a specific region of at least one input image portion from among the divided and resized input image portions of the first frame in the face detection operation, proceeding to a face tracking mode operation and performing a face tracking operation on a surrounding area of a specific region in a divided and resized input image portion of a second frame corresponding to the specific region in the at least one input image portion from among the divided and resized input image portions of the first frame in which the face is detected; and (d) when a face is not detected in the face tracking operation, proceeding to a partial detection mode operation and performing the face detection operation on a divided and resized input image portion of a third frame, the divided and resized input image portion of the third frame including a specific region in the third frame corresponding to the specific region in the at least the input image portion from among the divided and resized input image portions of the first frame in which the face is detected.