The “Light corrugated steel panel”, in this Report, is the thin steel sheet of 900-1200 m/m wide with longitudinal ridges, used chiefly for the partition of living quarter of merchant vessels and for the outside wall as the superstructure and the partition of living quarter of combatant vessels. It has been made clear, through many researches in various respect on this subject, done in the past, that “Light corrugated steel panel” is excellent in structure strength and very effective in reducing the weight of material used. With a view of ascertaining whether “Light corrugated steel panel” can be practicably used for the partition of steel vessels, i. e. through investigation of the butt-joint of “Light corrugated steel panel” and experiment with the model deck-structure made thereof, we have made further research with the result that its structural strength with fine finish has been proved quite satisfactory, while the man-hours worked as well as the weight of material used have been considerably reduced. We have, thus, decided to put this method to the actual processing and adopted for building the entire partition wall and upper-deck structures of 450 ton A Type Submarine chaser with the permission of Defence Administration. This report deals with the result of our research and experiment in this connection, the actual state of operation of the vessel built with this process and the stress to the super-structure made of “Light corrugated steel panel”.