The subject of analytical and numerical investigations in this paper is a metal seven-layer rectangular plate with a trapezoidal corrugated main core and two trapezoidal corrugated cores of faces. The hypothesis of deformation of the normal to the middle surface of the plate after bending and field of displacements is formulated. The plate is simply supported on all its edges and subjected to a uniform pressure. Equations of equilibrium are derived based on the theorem of minimum total potential energy and are solved with the use of the Galerkin method. The influence of the trapezoidal corrugation pitch of the cores on the deflection and the equivalent stress is analysed.