Randomness of ship's oscillations among waves is almost as the same as that of wave heights. Precisely speaking, even in one component of oscillation, namely rolling, randomnesses of amplitude, velocity, and acceleration are a little different to each other. This is because of response operator, as higher time differentials exaggerate high frequency part of wave spectrum, so that regularity increases from amplitude towards to velocity, acceleration, … If we prefer the irregularity of amplitude n =2, which means Rayleigh's distribution, for velocity becomes n =3, and for accelerantion n =4 for moderately rough sea surface. As waves grow up fully from seas to swells, these regularities gradually increase. The index number “n” is almost constant for every magnitude of maximum of oscillation, but if There are other strong resonances and there are several maxima in frequency distribution, we must consider regularity for these each component separately. The occurrence of “ n =2” is to he expected most frequently in the case of pitching and rolling amplitude.