A density interface is formed to σt=27.0 in Sea of Japan near Hokkaido. The nutrients in a surface of the density interface is a regular value through a year w ith a phosphate-P 0.8-1.0μg-at/l, nitrate-N 10.0μg-at/l and silicate-Si 15.0μgat/l. The depth of the density interface is formed becomes shallow in the westside and alsb the north side of Sea of Japan near Hokkaido.The internal waves thatpropag ates during surface of a density interface is concentrating on the offshore of Syak otan Peninsula and also Ohuyu Cape by the hydraulic model test.