The condition of a fishing boat is very different between her departure and arrival, i.e., between outward and homeward voyage, during fishing operation, before and after transshipping of fish from catching boat to fish carrier, and therefore her motions are also different. This paper deals with the rolling, pitching and heaving motions of the response oscillation of the ship under various sea conditions. A series of field measurements were carried out on board three bull trawlers (No.97 Choyo Maru, Nos. 23 and 51 Tokai Maru; 140 G.T.). The variation of each oscillation was recorded continuously for about 12 minutes in the 4 channel data recorder, while the sea conditions were observed by naked-eyes. The characters of oscillation such as rolling, pitching and vertical accelerations were obtained by the method of statistical analysis of the stochastic processes. Accordingly, the several substantial results are: 1) Although it is assumed that measured values of respective rolling, pitching and heaving motions under a certain sea condition are much the same, different values were observed. For instance, the rolling values in the bow sea under the pitching values in the head sea fluctuated under same sea condition. 2) During a fishing operation period (about 3 hours) the change of three motions is very small. 3) The rolling and heaving motions of the fishing boat in the fishing operation are greater than those in the voyage. However, the pitching is less conversely. 4) The author found a comfort index from the result of the measurment of vertical acceleration. The greater is the comfort index, the comfort becomes worse. The comfort, based on the comfort index, is the best in the fishing commander's bed and then in wireless operater's bed. There is a tendency that the comfort becomes worse in proportion tothe distance from the center of the ship.
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