A sifting device having four sieve-like layers for separating an unsoiled litter material from an animal waste comprises at least two nested trays configured to stack together. Each nested tray comprises a first screen tray and a second screen tray stackable and rotatable to each other, and each of the first and second screen trays has a base with a plurality of openings thereon. Each individual opening is sized to permit the unsoiled litter material to pass through, and to prevent the animal waste from passing through. The openings on the screen trays are arranged in a concentric, circular and intermittent manner. By rotating the screen tray, the sifting device can allow the unsoiled litter material to pass through or form an imperforate base by blocking all the openings. This provides an advantage of operation simplicity with minimized risk of clogging.
