A rearing cage unit is where an animal is reared individually in an environment at least including a space environment. The rearing cage unit includes an animal residential area that is defined by a floor, a ceiling, and a wall； an excrement collection area that is provided adjacently to the animal residential area； and an excretion sheet that is provided in the excrement collection are to receive excrement of the animal. At least one of the floor and the wall is made of a material including resin, and has an excretion hole that allows the excrement in the animal residential area to be discharged to the excrement collection area, and that has a size that prevents four feet of the animal from entering the excretion hole. The excretion sheet is provided facing the excretion hole.
