An illumination system includes first laser light sources, second laser light sources, an optical module, and a light homogenizing element. The first and second laser light sources respectively provide first and second beams. A light spot area formed when the second beams are emitted is different from that formed when the first beams are emitted. The optical module converts the first beams into spot-expanding beams which form a light spot area different from that of the first beams. The light homogenizing element includes a light incident face disposed on transmission paths of the second beams and the spot-expanding beams. A difference between light spot areas formed by the second beams and the spot-expanding beams on the light incident face is less than a difference between light spot areas formed when the second beams and the first beams are emitted. A projection apparatus having the illumination system is further disclosed.