A plant-cultivating method is provided which comprises a step (A) of irradiating a plant with a red light and a step (B) of irradiating a plant with a blue light, and a step (C) of irradiating a plant with a light predominantly comprised of far-red light wherein the step (A), the step (B) and the step (C) are independently and separately carried out for a predetermined period of time. The light irradiated at each of the steps (A), (B) and (C) has at least 60%, based on the total emission intensity of the light, of an emission intensity ratio of red light, blue light or far-red light.
