Most public guide robots installed in public spots such as exhibition halls and lobbies of department store etc., have poor capability to distinguish the users who require services. As to provide suitable services, public guide robots should have a human detection system that makes it possible to evaluate intention of customers from their movement direction. In this paper, a DPS (Directional Perception System) is realized based on face detection technology. In particular, to catch human movement efficiently and reduce computational time, human detection technology using face rectangle, which is obtained from the human face, is developed. DPS determines which customer needs services of public guide robots by investigating the size and direction of face rectangle. If DPS is adapted, guide service will be provided with more satisfaction and reliability, and power efficiency also can be added up because public guide robots provide services only for the users who expresses their intentions of wanting services explicitly. Finally, through several experiments, the feasibility of the proposed DPS is verified.