An animal rearing apparatus includes an animal rearing cage and a framework to which a plurality of side plates together forming the periphery of the animal rearing cage are detachably attached. At the bottom of the animal rearing cage, there are provided a bottom plate detachably attached thereto and defining a plurality of openings vertically extending therethrough and an excreta collecting portion for receiving and collecting animal excreta dropped through the openings of the bottom plate. The animal rearing cage has a ceiling thereof sectioned by a top plate or the excreta collecting portion belonging to an animal rearing cage on the upper stage. The framework or an attachment member thereof includes, at portions thereof corresponding in level to the ceiling of the animal rearing cage, engaging portions for detachably engaging and suspending engaged portions provided at upper portions of the respective side plates.