Wavelength sensor device for plant

Provided is a wavelength sensor device for a plant that is capable of handling a variety of growth elements of an object of growing condition measurement. A wavelength sensor device (10) for a plant is provided with a light emission unit (21) for emitting measurement light P to be irradiated onto an object of growing condition measurement (Cr), a light reception unit (22) for receiving reflected light (Pr) resulting from the reflection of the measurement light (P) by the object of growing condition measurement, and control units (23, 24, 25) for drive control of the light emission unit and light reception unit. The control units cause measurement light (P) of a wavelength band corresponding to a selected growth element (Eg) to be emitted from the light emission unit, cause the reception unit to receive reflected light (Pr) resulting from the reflection of the measurement light (P) of each wavelength band corresponding to the selected growth element (Eg) by the object of growing condition measurement, and determine the reflected light amount from the object of growing condition measurement for each wavelength band corresponding to the growth element (Eg).