1. A device for estimating a head pose, the device comprising: a processor configured to control one or more processor-executable units; a head area extractor configured to extract a head area comprising a head from an input depth image, the head area extractor comprising: a head detector configured to detect the head area from the input depth image based on a depth feature of the head; and a background remover configured to remove a background part from the detected head area based on a depth difference between the head and the background part; a head pitch angle estimator, comprising: a pitch line extractor configured to extract a pitch line of the head; a filter configured to classify the pitch line into sections and to obtain a straight line in a section of the sections having a highest fitting probability; a pitch angle calculator configured to calculate a pitch angle of the head based on the straight line; a head yaw angle estimator configured to estimate a yaw angle of the head in the head area; and a head pose displayer configured to display a head pose based on the calculated pitch angle of the head and the estimated yaw angle of the head.