A fly-eye lens group, a light source device, and a projection apparatus. The fly-eye lens group includes: a first fly-eye lens, a second fly-eye lens, and a third fly-eye lens. The first fly-eye lens is parallel to the second fly-eye lens, the first fly-eye lens is perpendicular to the third fly-eye lens, a double fly-eye structure is formed by the first fly-eye lens and the second fly-eye lens, and the third fly-eye lens and the first fly-eye lens also form a double fly-eye structure. The fly-eye lens group is used for homogenizing incident first excitation light, excited light, and second excitation light.