This is the 6th (final) report of the studies on the orthogonally stiffened plate. In this report, it is given the solution of the orthogonally stiffened box type structure, while the experiment of large scaled box structure is carried out. Comparing the observed deflections and stresses with the values derived from this theory, it is shown that orthogonally stiffened box type structure can be also expressed by this theory as concluded in the preceding reports.