PURPOSE: To obtain a substrate for planting sea weeds, which is installed on the sea bottom, capable of reviving a sea area, etc., of a withered seashore and growing and proliferating useful sea weeds such as tangle, excellent in workability of cultivation of sea weeds and capable of attaining labor saving.

CONSTITUTION: The objective substrate is constituted by using a metallic material of a chain made of steel, etc., as a main component and connecting these materials in a state of net. One side of net-like space of the substrate is 20-200cm and the substrate has deformable property capable of following ruggedness of the sea bottom, strength capable of withstanding waves and weight which is not moved and carried away. The substrate can be sunk in a desired sea area by attaching floats to the substrate to float the substrate and towing the floated substrate and useful sea weeds attached and grown thereto can be harvested by floating the substrate and substrate face to which sea weeds were attached can be renewed by pulling up the substrate on the land, allowing the substrate to stand and dyeing out attached organisms.