Based on the finite deformation theory of thin shells and by the application of Galerkin's method, an approximate analysis is presented for the postbuckling behavior of a finite thin curved panel (a part of circular cylindrical shell) which is compressed parallel to the generator and simply supported all around. Here it is assumed that the form of deflection is expressed by a trigonometric function multiplied by the double trigonometric series. Numerical calculations are carried out for the case where the length of the sides of the panel is equal to that of the loaded edges. The trigonometric series is truncated after the first four terms. The uniform compressive load is plotted versus the displacement at the center of the loaded edges and the deflection at the center of the panel for a range of the curvature parameter. The classical buckling load is also shown against the curvature parameter.