A minimum compliance design technique of plate thickness variance for general shell structures assembled by linear-or curved-shell elements is proposed. In this technique, the shell structures are discretized into isoparametric finite shell elements, and nodal point thicknesses are taken as design variables. Thickness distributions on subregions of each element are interpolated by quadratic shape function using the nodal values. Therefore, one can obtain optimal design in which the thickness varys continuously over the whole region of the shell structure. A mathematical programming method is employed to solve the optimization problems using design sensitivity analysis. As a check on effectiveness, the proposed method is applied to a classical cantilever beam problem and a plate clamped at two corners. Furthermore, the problem of maximizing the torsional rigidity of the motorcycle body, which consists of shell elements, is solved.