Many types of quadrilateral plane element are studied in literatures on FEA and implemented in various computer programs. Field engineers use these elements in their new projects according to the manual which is supplied with the program purchased, such as SAP2000, MIDAS, and so on. However, since these computer programs only present the concept and the way of using the commands and give different results in the same structural analysis model according to the element provided by each program, it is difficult to understand the basic theories and differences between these elements. So, it is necessary to establish the basic theories and the programming techniques in common use to consider these elements. In this study, basic theories for the consideration of quadrilateral plane elements with several degrees of freedom are studied first, where some of possible methods are investigated. On the basis of these theoretical backgrounds, an algorithm available in computer program is derived, which calculates the stiffness matrix of these elements in one process, and then a computer program(sNs) is developed based on the theory and algorithm studied. Lastly, some examples using these computerized elements are performed and the analysis results are compared with other commercial-use structural analysis programs used in field engineering for the verification of its fitness and validity.