A light combination device includes a reflective element and a first color separating element. The reflective element guides first color light beams emitted from at least a first light source and a second light source to propagate in a first direction. The first light source and the second light source are differently positioned in a space. The first color separating element transmits the first color light beams and reflects second color light beams emitted from at least a third light source and a fourth light source. The third light source and the fourth light source are differently positioned in the space. The first color separating element has a coating curved surface, and a curvature of the coating curved surface is varied according to positions of the third light source and the fourth light source to guide the second color light beams to propagate in the first direction.