In a shipyard, skilled workers bend shell plates by the heat line bending process, a bending roller and/or a press. While the shell plate whose curvature is small and slowly changing can be bent under its own weight, no theoretical investigations have been carried out into the bending of plate under its own weight. In the paper, the authors carried out both theoretical and experimental investigations into the bending of shell plates on multiple supports under their own weight for the purpose of practical applications of the bending to the shipyard operation Principal curvatures of shell plates of a ship are calculated and then the concepts of curved surfaces with uniform curvatures are introduced into the analyses of the bending. It is clarified that the parameters t ²/ R ₁ and t ²/ R ₂ exert decisive influences on the bending. The bending of plates on multiple supports under their own weight are analysed by the finite element method. And the relations between t ²/ R ₁ and t ²/ R ₂ for the application of the bending are obtained through the analyses. At the stage of assembly, measurements are taken of the configuration of shell plates bent under their own weight and those bent by a bending roller and the heat line bending. And the accuracy of the bending of shell plates are clarified.