In 1968, Ueda and his colleagues developed the new mechanism of plastic hinge based on the incremental theory of plasticity and derived the elastic-plastic and plastic stiffness matrices for one-dimensional members. Using this plastic hinge, a method of elastic-plastic analysis of space-framed structures was well developed including the effect of large deflection. In this paper, extending the basic idea of this plastic hinge method, a new method for plastic analysis of plates and solid bodies is developed. The basic theory of the new method is presented using the ordinary finite element method (the stiffness method). In this theory, the yield condition at the ith node of an element is described as follows: “The ith node becomes plastic when the resultant stresses at this node satisfy the appropriate plasticity condition and the plastic deformation is developed only at the nodes”. In this sense, the authors named this method the ‘Plastic Node Method’. For the element with k plastic nodes, the relation between the increments of the nodal force, d x, and the nodal displacement, d u, is derived in the following form: dx = K p du. K p in this equation is either elastic-plastic or plastic stiffness matrix and is expressed in explicit form. When an element is subjected to constant strain, the element becomes plastic in the entire volume if the yield condition is satisfied at any point. Simultaneously, the plastic node is formed at every node of the element. Completely the same plastic stiffness matrix is obtained by either the ordinary finite element method or the present plastic node method. A similar fact is observed when a plate element is subjected to uniform bending. From these facts the accuracy of the solution by this method is anticipated to be the same order as that by the ordinary finite element method when the element division increases. The plastic node method is quite general for plastic analysis since this can be applied to a continuum of any geometrical shape, and example analyses by this method demonstrate the validity and usefulness of the method.