Only a few studies related to the manoeuvring characteristics of fishing vessels have been reported, because most fishing vessels are not subject to the International Maritime Organization(IMO) manoeuvrability standards. In addition, since the construction scale is smaller than that of merchant ships, empirical formulas, rather than model tests, are use to predict the manoeuvring characteristics at the design stage due to time and budget savings. Nevertheless, because no empirical formula is developed for fishing vessels, the empirical formula developed for merchant ships is applied in its place. However, since the characteristics of hull shape parameter in particular and of fishing vessels and merchant ships are clearly different, prediction errors will occur. Therefore, in this study, the modified empirical formula was derived by including the characteristic parameters of target fishing vessels in the Kijima et al.(1990) formula to improve the accuracy in predicting the manoeuvring characteristics of the target fishing vessels. Simulating the turning-motions of the target fishing vessels using the modified empirical formula yielded an average error of 6% compared with the sea trial test of full scale ships. Hence, our results reproduce the test data more accurately than the Kijima et al.(1990) formula. In the future, the modified empirical formula derived through this study will enable a prediction of the manoeuvring characteristic of fishing vessels at the design stage and an improvement in ship safety and fishing efficiency in the narrow fishing port or in the fishing ground.