Large contact force fluctuations between contact wires and pantographs cause unstable current collection conditions and so it is important to measure and estimate the contact force to obtain a better knowledge of current collection quality. Contact force waveforms are affected by the condition of equipment used on overhead contact lines, so it is to be expected that the contact force waveform represents the state of repair of an overhead contact line. This paper describes contact force waveform characteristics against the static height of Shinkansen contact wires and their application in overhead line diagnosis.