Provided are a plant cultivation system, device, and method for simultaneously producing wide variety of plants such as leaf vegetables, fruit vegetables, head-forming vegetables, and legumes year-round without causing continuous cropping injury by circulating a simple nutrient solution. In each of the plant cultivation system, device, and method, a temperature of reformed air, which is obtained by reforming air into a state suitable for setting a dissolved-oxygen concentration of the simple nutrient solution in a cultivation tank for holding a wide variety of plants to a predetermined concentration, is set to a predetermined temperature, and the reformed air is supplied, at a flow rate required for setting the dissolved-oxygen concentration of the simple nutrient solution to the predetermined concentration, from a vicinity of a bacterial colonization portion into the simple nutrient solution flowing at a predetermined speed through the cultivation tank.
