This study presents a geometrically nonlinear F. E. formulation using the improved curved beam element. The total and updated Lagrangian approach is applied in large deformation analysis and the isoparametric beam element degenerated from the plane stress element is utilized. The existing curved beam element formulations are restricted to small rotation increments in the incremental analysis. The element formulation presented in this study removes such a restriction. This is accomplished by retaining second order rotation terms in the incremental displacement field and including the effects of those rotation terms in the derivation of the tangent stiffness matrices. Also, an iterative load / displacement incremental method for non-linear finite element analysis of the plane framed structure is applied. Numerical examples are presented to demonstrate the effectiveness of the proposed beam element and the feasibility of the present load / displacement incremental method for non-linear analysis of the plane frames and arches.