A plant-cultivating method is provided which comprises a red light irradiation step (A) and a blue light irradiation step (B), wherein the step (A) and the step (B) are independently carried out for a predetermined period of time under cultivation conditions such that a fertilizer is used at each of the step (A) and the step (B), of which at least the fertilizer used at the step (B) is applied in the form of a nutritious liquid containing fertilizer ingredients and further an increased amount of dissolved oxygen, which nutritious liquid is prepared by adding oxygen therein. Preferably, a nutritious liquid is applied at each of the step (A) and the step (B), and the nutritious liquid applied at the step (B) contains dissolved oxygen at a content higher than that in the nutritious liquid applied at the step (A).
