PROBLEM TO BE SOLVED: To provide a method for producing seed of brown algae and a method for producing a sea weed bed using the seed-producing method. SOLUTION: Spores collected from mother body of a brown algae are stored in a dark cold place for an arbitrary period and the stored spores are grown to young sporophytes to obtain the seed of brown algae. The produced seeds are attached to a proliferation base on the shore and a plurality of the proliferation bases are sporadically distributed in the sea to form a sea weed bed.