The present disclosure relates to an image-based component measurement system using a light unit that outputs a variable wavelength, a method thereof, and a plant cultivation method using the same. More specifically, the present disclosure provides an image-based component measurement system using a light unit that outputs a variable wavelength, a method thereof, and a plant cultivation method using the same, which collect and analyze data based on image information acquired by emitting light having a specific wavelength using a sheet on which a plurality of quantum dots which can be controlled to have a wavelength necessary for measuring a configuration component of a target object are arranged. Thus, the system and methods are able to measure component content contained in the target object using a low cost and miniaturized device, and cultivate a plant by adjusting content of nutrients of the plant using the measured component content.