It has become very important to study the lightning surges that flow into telecommunications equipment because of the increased use of circuits susceptible to excess voltage. This paper reports for the first time simultaneous measurements of distributed lightning current at many positions in a mountain-top radio relay station caused by natural direct lightning strikes. More than 90% of the direct lightning current flowed from the lightning rod to the ground through building structural components such as antenna tower legs, waveguides, and so on, with the high frequency components of the lightning current tending to flow into the outside parts of those structural components. And then, 25 to 43 % of the lightning current flowed out again to outside telecommunications cables and power lines because the lightning current raised the station's ground potential. Based on these measurements, to help predict lightning current which is dangerous to telecommunications equipment, lightning current occurrence probabilities at the waveguide and cables were estimated by analyzing the distribution ratios between the current in those components.