This paper introduces the non-contact vibration measuring system known as U-Doppler that has recently been developed by the RTRI. In the field of railway structure monitoring, dynamic characteristics estimated by vibration measurements are applied to evaluate structural integrity. Adopting a long-distance remote measurement method with U-Doppler enables improvement of the efficiency and safety of measurement, since it is unnecessary to install sensors and cables at locations high above structures and remove them later. This report first gives an outline of U-Doppler and its measuring method. It then goes on to verify the accuracy of U-Doppler using the results of laboratory experiments, microtremor measurement of a rigid-frame viaduct, impact vibration measurement of a bridge pier, and deflection measurement of a bridge girder.