A phosphor device of an illumination system emitting a first waveband light includes a substrate and a phosphor layer formed on the substrate. The phosphor layer includes a first phosphor agent and a second phosphor agent. The first waveband light is converted into a first color light by the first phosphor agent. The second phosphor agent is distributed over the first phosphor agent and mixed with the first phosphor agent, and the first waveband light is converted into a second color light by the second phosphor agent. The first color light and the second color light are integrated into the second waveband light. The difference between the first wavelength peak of the first color light and the second wavelength peak of the second color light is 50 to 100 nanometers. Therefore, the advantages of increasing the purity, the luminance and the luminous intensity of specific color light are achieved.