A shell plating developing method leading to reduction of the amount of machining and improvement of the efficiency in manufacturing the shell plating. In the shell plating developing method, a shell plating lattice system is constituted, the directions in which the curvature of a shell plating (P) at each lattice point of the shell plating system is maximum and minimum are determined (s102), a first connection line (L1) and a second connection line (L2) extending in the direction, out of the directions, in which the absolute value of the curvature is large and small are determined (s104), the first connection line (L1) is developed as a straight line on a flat plate (P") while the length of the first connection line (L1) is maintained, and the second connection line (L2) is developed as a line perpendicular to the line on a flat plate (P") in such a way that the integrated value of the amount of machining corresponding to the extension ratio or the shrinkage ratio of the second connection line (L2) is minimum.