A wavelength conversion device includes a substrate, a reflective member, and a wavelength conversion member. The reflective member is disposed on the substrate and includes a continuous-phase material and nano particles. The nano particles are distributed in the continuous-phase material. A refractive index of the continuous-phase material is different from a refractive index of the nano particles. The wavelength conversion member is disposed on the reflective member. The reflective member is configured to reflect the light converted from the wavelength conversion member to output.