This paper describes a measurement method for longitudinal displacement of wheel/rail contact point in a railway vehicle using a wheelset to measure the wheel/rail contact forces, which is generally used for the sake of the running safety evaluation in Japan. The clarification of phenomenon related to the wheel/rail contact has very important role to discuss the curving performance and the running safety of railway vehicles. The longitudinal displacement of the contact point is related to the wheelset angle of attack, which is related to the steering performance of the wheelset. The authors propose algorithms to extract informations about the contact point from the cyclic signal of the strain gauges that are put on the wheel to measure the contact forces. Experiments on roller rigs were carried out to evaluate the reliability and the accuracy of the proposed algorithm. The running tests were also carried out to demonstrate the applicability of the proposed algorithm to the real condition used. Those test results show that the measurement result using proposed algorithm is reliable as a longitudinal displacement of the contact point.