It is known that a loading condition of fishing vessel changes frequently by fish catching and fuel oil consumption. This paper describes the study on influence of loading condition on drifting motion of fishing vessel in a regular wave. In previous paper, model experiments were carried out and it was shown that the trim condition of vessel affects the beginning of drifting motion. In this paper, the characteristics of steady drifting motion in a regular wave were examined by numerical simulation based on experimental data of forces acting on a hull. As the results, it was found that the trim condition of vessel affects the speed and direction of drifting motion. Especially, according to the incident angle of wave, the direction differs significantly. Therefore, it is important to consider the trim condition of vessel for the prediction of drifting motion.