Although the wear of contact wire is one of the most important problems for maintenance of an overhead catenary system, the wear mechanism of the contact wire is very complicated, and many unsolved problems still exist. The authors are studying in the quantitative effect of the pantograph contact force and the arc due to contact loss on the contact wire wear. For this purpose, the authors have developed a method, by which contact forces of all pantographs measurable during passing on sections where sensors are installed on the catenary. The method is effective in monitoring the behaviors of the pantograph. The authors have measured the contact forces and arcs on the line test. In this paper, the authors have reported the results of measuring the contact force on the line test. This result has indicated that the foregoing measurement method with sensors on catenary is properly valid.