In this report, a synthetically improving method of fishing vessel's performances is proposed. Present method is composed on the evaluations of seaworthiness, stability, workability and propulsive performance. Wave resistance of propulsive performance is the most important to determine the fishing vessel's hull form, but it is difficult to estimate quantitatively. Wave resistance is mainly depending on ships'length, prismatic coefficient and sectional area curve, so it must be fixed these three design parameters in terms of the confirmation of minimum wave resistance before present method takes place. After these three design parameters were fixed, taking the improvements on seaworthiness, stability and workability as a constraint, present method decides water line breadth, draft at P.P.s and block coefficient in which the summation of the viscous resistance and resistance increase in waves minimizes. In the application example for the 439-ton type tuna longliner, the reduction of 1〜3% can be expected in effective horse power.