This paper describes a method of measuring moving objects and estimating human behaviors in a room using only one laser range finder (LRF) installed in the room and a strip of mirror attached to a side wall close to a floor. The area of sensing is limited to a plane parallel to and just a few centimeters above the floor, thus covering the whole room with minimal invasion of privacy of a resident while reducing occlusion. The important feature of the measurement consists in processing of both distance and reflectance acquired by the LRF from the surface of the existing objects. This enables immediate distinction of clusters of objects made of different materials in the analysis of the scene cluttered with objects. The human behavior models are effectively utilized to estimate human behavior from LRF data. The experimental results validate the effectiveness of the proposed method.