The present paper proposes a methed for the elastic-plastic analysis of plate bending problems using the finite element method. In the present method plastic deformations are idealized according to the concept of plastic hinge lines, while the conventional finite element procedure is employed before yielding occurs. Morley's plate bending element is used herein because of its simplicity. Plastic analysis is based on the assumption that plastic bending deformations are concentrated in plastic hinges along the element boundaries. In order to decrease dependancy of calculated results on mesh idealization, simple automatic mesh re-subdivision is implemented in the procedure. This method overcomes the following two difficulties in the ordinary finite element method; time consuming numerical integration of stiffness matrix along plate thickness and overestimation of stiffness due to shape functions with too strong compatibility conditions for localized plastic deformations. Basic numerical examples are studied to verify the validity of the present method.