PROBLEM TO BE SOLVED: To obtain a synergistic effect by carrying out an artificial cultivation of a single species of an aquatic plant and a cultivation of aquatic animals in the same nutrient solution. SOLUTION: A technical means for artificially providing a condition adjusted to a single individual of an aquatic plant is adopted. A technical means for generating carbon dioxide and a nutrient required for an aquatic plant by cultivating the aquatic plant using the same nutrient solution for the culture of an aquatic life and using carbon dioxide and the nutrient is adopted.