Recently, tracking and counting people are requested for the security purpose. In this paper, we propose a method to track and count people with Laser Range Finders. A method to extract the walking human from the sensor data is introduced. Multi-target model and Kalman Alter based estimation are employed to track the human movement and count the number of people. The proposed method is applied to a novel system to monitor the entrance area and to filter out the trespasser who enters the door without identification. Experiments for various cases are performed to verify the usefulness of developed proto-type system.