An object is to provide a plant illumination apparatus that can output light having a high degree of circular polarization in the target wavelength range. This object is achieved by having a reflective-type polarizing plate having an effective wavelength range, a light-emitting device, and a reflective plate configured to reflect light emitted from the light-emitting device and satisfying:λ1 >； λ2, λ2 >； λ3, and w >； 30 nmwherein λ1 is the center wavelength of the effective wavelength range of the reflective-type polarizing plate, λ2 is the center wavelength of the light-emitting device, w is the full width at half maximum of the transmittance of the reflective-type polarizing plate, and λ3 is the shorter wavelength of the wavelengths at the full width at half maximum.
