The recent development in high speed digital computers has been giving favor to a numerical approach, termed “the finite element method”. In the previous paper, the method has been expanded to analyse elastic-plastic buckling of plates and the authors furthermore developed the finite element method to buckling of stiffened plate. In most stiffened plates, plates are reinforced on one side. Then, the neutral plane of the stiffened plate moves away from the middle plane of the plate and additional stresses on the plate are induced in the instant of buckling of the stiffened plate. By the method, the effect of one side stiffening can be taken into account as well as torsional and axial rigidities of the stiffeners. As a basic example of the application, the accuracy of the solution by the method was examined for several kinds of stiffened plates under compression in relation to the number of finite elements. And compressive buckling strength of a stiffened plate was analyzed, varying the direction of the stiffener. The results were quite satisfactory in comparison with analytical solutions and indicated the usefulness of the method.