A calculation method of the transmitted wave height and the reflected wave height by the oscillating cylinder moored in regular beam waves are developed first. Secondly, the theorctical calculation results of transmitted wave height, not only for restrained condition but also for oscillating condition, are compared with model experiments. Thirdly, according to Maruo's theory, the drifting forces acting on the circular cylinder heaving in beam waves are calculated by using the theoretical reflection coefficient obtained by this study and compared with Maruo's computation results. Conclusions of the present study are summarized as follows: 1) Calculated theoretical results of transmission coefficients are in good agreement with model experimental ones. 2) At the resonant frequency of oscillation, the value of transmission coefficient and reflection coefficient is respectively equal to the reflection coefficient and transmission coefficient for restrained condition. 3) Drifting forces calculated by Maruo's theory and the exact values of reflection coefficient show a different tendency from the Maruo's computation results, and the value of drifting force at the resonance condition does not show maximum value such as Suehiro's experimental results. Accordingly, it results that Maruo's theory for drifting force can not explain the experimental results.
