A lighting device includes a lighting unit emitting an output light having a light spectrum. The light spectrum in a range from 520 nm to 780 nm has a main peak, and the light spectrum in a range from 400 nm to 470 nm has a sub peak with a maximum intensity at a first wavelength. A first sub peak integral is an integral of the light spectrum calculated from a wavelength of the first wavelength minus 20 nm to the first wavelength. An intensity integral of a main wave having the main peak in the light spectrum is calculated from 521 nm to 780 nm, and a ratio of the first sub peak integral to the intensity integral is in a range from 0.05 % to 2%.