PURPOSE: To eliminate the need for positioning and attaching operations for projections, by a method wherein cavities for forming projections are previously formed in dies for molding an FRP hull so that projections can be formed simultaneously with the manufacture of a hull.

CONSTITUTION: Cavities for forming projections 3 are previously formed in dies 13 and 13' for molding a hull outside plating 1. A skin 31 of fiber-reinforced plastics or the like is laminated in each cavity, and a core material 32 of urethane foam or the like is filled inside thereof. Then, a side outside-plating 1 is laminated. Thereby, the projections 3 such as bulge, bilge keel and the like, attached to the sides of a hull, are formed simultaneously with the molding of the hull.