1. A person clothing feature extraction device using a processor and a clothing feature storage configured to store clothing features based on an input video, the person clothing feature extraction device comprising: a person region detection part configured to automatically detect a person's region from the input video by performing a person detection image processing operation; a person direction determination part configured to automatically determine a person's direction of the person's region by performing an image processing operation; a clothing segment separation part configured to automatically determine a separability of person's clothes in the person's region based on shape analysis of the person's region and the position of the person's region using background prior information indicating a part of a person is visible, and configured to automatically produce clothing segment separation information including information whether or not the person's region can be separated into segment regions and information describing segment regions from which clothing features are to be extracted; and a clothing feature extraction part configured to extract the clothing features representing visual features of person's clothes from the segment regions of the person's region defined by the clothing segment separation information as clothing features corresponding to the person's direction, thus storing the clothing features in the clothing feature storage.