A wavelength conversion device, etc., for laser light according to the present disclosure includes: a first substrate that is light-transmissive; a second substrate that is light-transmissive; and a phosphor layer provided between the first substrate and the second substrate and including a phosphor that converts the wavelength of incident laser light having a predetermined wavelength. The laser light has a laser irradiation power density of at least 0.03 W/mm2, and each of the first substrate and the second substrate has a thermal conductivity higher than the thermal conductivity of the phosphor layer.