The authors have been examining the effectiveness of an artificial foundation for kelp bed at a sandy sea bottom off the west coast of Miura Peninsula, central Japan. This paper aims at showing a structural design method of artificial foundations for kelp bed. In this paper, described are the design wave condition according to wind wave prediction in this sea area, the structure of the artificial substratum foundation based on hydraulic model experiments and surface form of an artificial algal substratum suitable for adhesion of zoospore found out in a sense of tests both in the field and laboratry.