Using a radio controlled model, the experiment succeeded to realize broaching-to phenomena on a small high speed boat in the model basin stably. The broaching-to always occurs when the ship is under surf-riding condition on the front slope of waves and the velocity of ship reaches to almost the same as that of the wave propagation. Through the parametric tests, it was made clear that the most likely conditions are λ/ L =2.0, χ=20°-30° and U cosχ= V _w . Many items of measurements were conducted and behavior of the model ship during the broaching-to was recorded. In order to analyse the brcaching-to phenomena, the AIC evaluation technique was applied to the problem. As the result, the optimal form of the manoeuvring equations was derived and each coefficient was identified. Dynamic balance of each component in broaching condition was discussed. Experimental results in the model basin were compared with those of the ship in seas during the broaching-to. It was recognized that both records were similar in pattern and agreed well in quantity.