A culture rack (10) is disposed in a culturing area (3) of which a water level is adjustable so that the culture rack (10) has a predetermined height from a bottom surface of the culturing area. Organism to be cultured (8) such as shellfishes are placed on the culture rack (10), and the water level of the culturing area (3) is adjusted. Thus, the water level is controlled to realize: a dry state in which the organisms to be cultured (8) on the culture rack (10) are exposed from a water surface and an in-water state in which the organisms to be cultured (8) are submerged in the water. Like this, the most suitable water level for survival and growth of the organisms to be cultured (8) is provided to shorten the culture period and to reduce depletion in the high water temperature period.
