The unevenness of contact lines is one of the factors that considerably influences on the dynamic characteristics of current collection system. In order to analyze the influence of the contact line unevenness on the fluctuation of the contact force between contact line and pantograph, an instrument was devised to measure the unevenness of contact lines accurately and continuously. The instrument consists of two pairs of laser sensors for the purpose of reducing measurement errors by the vertical vibration of measurement vehicle. This paper describes the measuring method of contact line unevenness, reports some examples of the measurement of real lines, and proposes a method to evaluate the conditions of overhead equipment.