A phosphor device of an illumination system is provided. The illumination system emits a first waveband light and has an optical path. The phosphor device includes a first section and a first phosphor agent. The first phosphor agent is coated on the first section. After the first waveband light is received by the first phosphor agent, the first waveband light is converted into a third waveband light, and the third waveband light is directed to the optical path, so that the third waveband light is separated into at least two color lights along the optical path.