This paper describes a converting algorithm between programmable languages of a software PLU. It is based on IEC 61131-3 standard and PC. The proposed control logic is designed by the software model and common element with data type, variables, POUs(program organization unit) and execution control unit commonly used within programmable languages of IEC 61131-3 Standard. The generation method of object file is proposed on five programmable language based on IEC 61131-3. It is represented as fo11ows; 1) the generation method using conversion algorithm from LD to IL with FBD(function block diagram), 2) the generation method using f code generation algorithm from SFC using the SFC execution sequence with FBD and ST(structured text). The proposed control logic generator was implemented by Visual C++ 6.0 and MFC on MS-windows NT 4.0.