Recently, a lot of free form buildings, which have irregular structural shape, are constructed frequently in our country. In such buildings, there are many curved beams and columns which have non-prismatic sections occasionally. But, many computer programs commonly used in practice like SAP2000 do not any finite elements available for the structural analysis including these curved members. So, many structural engineers necessarily use the segmented straight-line beam elements for their curved frame members. It makes the inconsistency between analysis model and real structure. Therefore, in this study, a theoretical background of a general curved beam element describing the bent frame member is studied first, then some formulas available in computer programming are derived on the basis of the theoretical background. A computer program, named sNs, was developed using these formulas, and analysis results by sNs are compared with those by some commercial programs and theory.