The problem of wave overtopping is very important in the design of protective shore structures. Many researchers have made model experiments to obtain the quantitative characteristics for various structure types under various wave conditions, and estimation of the rate of wave overtopping for a particular condition is made by interpolation of curves established by those model experiments. However, some model experiments have demonstrated the existence of large scale effect in the phenomena of wave run up, which is also related to the rate of wave overtopping. The rate of wave overtopping directly affects to the facilities just behind the protective shore structure, i.e. the wave absorbing revetment in this paper, or to the stability of the structure itself. The authors have made direct observations of the rate of wave overtopping in the field in 1971 and 1972. The rate of wave overtopping was observed by special equipments which were set just behind wave abosorbing revetment. Moving pictures of the condition of wave overtopping were taken, and the effect of wave overtopping of a particular rate on the structure or on the facilities behind the revetment was analyzed. The rate of wave overtopping obtained by the direct field observation was within the range of 10-6 — 10-4 m3/m/sec. The effect of the wave overtopping of which the rate is 10-3 – 10-2 m3/m/sec was also evaluated with the examples of two disasters occurred in 1972.