We are conducting the research project named "Robot Town Project". The aim of this research is to develop a distributed sensor system and its management system so that robots can work with humans in an ordinary environment for daily human life. However, it is difficult for distributed sensors to cover all of the environment. This paper describes a method of cooperative tracking of pedestrians by an on-board Laser Range Finder (LRF) of mobile robot and a fixed sensor. The method successfully expands the area of sensing, and reduces the occlusion. The fixed vision measures the position of the mobile robot in the world coordinate system, and the on-board LRF measures the relative position with the mobile robot of pedestrians using Kalman filter. Integrating these information, this system can track pedestrian in the world coordinate system.