The purpose of the present study is to develop a person counting system using a 3D laser scanner. The system consists of a person-detection component, a tracking component, and a counting component. The person-detection component detects human bodies as a point cloud, even if a number of people are close to each other. To achieve this, we use a method of grouping the point cloud towards the bottom from the top. The tracking component tracks the detected person using a Kalman filter. The counting component counts the number of people who enter and exit a structure. Experimental results obtained in the present study reveal that the proposed system can recognize individual pedestrians and count the number of people passing through crowded outdoor environments.