A litter box for cats or other domestic animals, which comprises three pans insertable into each other to form a stack. The position of the pans is interchangeable and each pan has openings in its inferior part for filtration of an absorbing material used to solidify and absorb the organic wastes. The openings of each pan are located at positions different from the openings of the other pans in such a manner that the openings of each pair of adjacent pans be vertically out of line. One advantage of this litter box is that it is not necessary to use a shovel to pick up and dispose of the organic wastes.