An illumination apparatus includes a first light-emitting device, a second light-emitting device, and a third light-emitting device. The light emitted from the third light-emitting device is selectively mixed with the light emitted from the first light-emitting device or the second light-emitting device to form a white light having a chromaticity coordinate point substantially located on a Black Body Locus. A color of the light emitted from the third light-emitting device is determined by linear relationships between chromaticity coordinate points corresponding to wavelengths of the lights emitted form the first light-emitting device and the second light-emitting device and corresponding to a color temperature of the white light. A method for generating a white light is also disclosed herein.