In the previous papers, the authors applied the transient response method to pure heave motion, pure pitch motion and coupled motion and showed the effectiveness for ship research. The experimental results obtaind by this method, frequency transfer functions and hydrodynamic derivative coefficients, were affected by side wall effect due to the reflection from the tank walls of waves generated by motions of the ship model.By using the Hanaoka's theoretical calculations on the angle of a travelling wave sector formed by motions of the ship model, Vossers & Swaan offered a practical chart on side wall effect in waves.In this paper, the waves were measured near the oscillating ship model running in still water at a given speed and the relationship among the reflected waves, model speed, the ratio of tank breadth to ship model length and the frequency of oscillation was investigated.The authors could certify that the frequency range in which the ship model would be influenced by side walls could be predicted practically by using the Vossers & Swaan's chart.