PROBLEM TO BE SOLVED: To provide an apparatus for multistage continuous cultivation of marine algae, surely performing transfer of the marine algae between multistage culture tanks, improving productivity per unit area or unit volume, lowering the total facility height of the multistage culture tanks, reducing the apparatus cost, installation cost and operation cost, and producing the marine algae in high productivity at a low cost.SOLUTION: The multistage culture apparatus is provided with multistage culture tanks comprising a plurality of culture tanks having an areal ratio or volume ratio between the front and rear culture tanks successively increasing according to the growth ratio of the cultured marine algae and lowering the installation level of the each culture tank stepwise, and a transfer pipe connecting the bottom part of the each culture tank to the latter stage culture tank and having an on-off valve. Transfer of the marine algae between the front and rear culture tanks is carried out by opening and closing the on-off valve of the transfer pipe to cause natural flow down of the culture seawater by gravitational force. The areal ratio and the height of each culture tank are adjusted in a manner that the total installation height of the multistage culture tanks is decreased when forming steps to keep the bottom face level of the front stage culture tank to be not lower than the water level of the latter stage culture tank when transferring the marine algae in the front stage culture tank.【課題】多段式養殖槽間の海藻類の移し変えを確実に行い、単位面積又は容積あたりの生産性を向上させ、多段式養殖槽全体の設備高さをより低くでき、設備費、その建設費、運転費の安い、経済的で生産性の高い海藻類の多段式連続養殖装置を提供する。【解決手段】前後段の養殖槽の面積比又は容積比が養殖する海藻類の生長率に応じて順次拡大しかつ各養殖槽の設置レベルが段階的に下げられた複数の養殖槽で構成される多段式養殖槽と、各養殖槽の底面部と後段の養殖槽との間を連結する開閉弁付きの移送配管と、を備え、前後段の養殖槽間の海藻類の移し変えを、移送配管の弁の開閉により、重力による養殖海水の自然流下を利用して行い、前段の養殖槽の底面レベルを前段の養殖槽内の海藻類の移し変えを行った時の後段の養殖槽の水面レベル以上となるように段差を設けた時の多段式養殖槽全体の設備高さがより小さくなるように、面積比及び各養殖槽の高さを調整してなることにより、上記課題を解決する。【選択図】図１
