Provided is an organic light emitting device. The organic light emitting device comprising a first light emitting part on a substrate, emitting a first light of a first wavelength, wherein the first light emitting part includes a transparent first electrode, a first organic light emitting layer, and a transparent second electrode sequentially stacked on the substrate, a second light emitting part on the first light emitting part, emitting a second light of a second wavelength, wherein the second light emitting part includes a transparent third electrode, a second organic light emitting layer, and a reflective fourth electrode sequentially stacked on the first light emitting part, and a fluorescent material disposed at least one between the substrate and the first light emitting part, and between the first light emitting part and second light emitting part.