An animal litter box comprising: a lower container (30, 30A, 30B, 30C, 30D) of which a top portion is open, the lower container (30, 30A, 30B, 30C, 30D) having a lower bottom portion and a lower side wall portion provided upright from a periphery of the lower bottom portion; and an upper container (20, 20A) of which a top portion is open, the upper container (20, 20A) being placed on the lower container (30, 30A, 30B, 30C, 30D), wherein the upper container (20, 20A) includes: an upper bottom portion in which a plurality of through holes is formed; an upper wall portion provided upright from a periphery of the upper bottom portion; and an extension wall portion extending downwardly from an outer face of the upper wall portion, and wherein a lower end portion of the extension wall portion is positioned below the upper bottom portion, characterised in that: a foot portion (231, 231A) is provided, which contacts with an installation surface on which the lower container (30, 30A, 30B, 30C, 30D) is installed in a state in which the upper container (20, 20A) is placed on the lower container (30, 30A, 30B, 30C, 30D), and a cutout portion is provided to expose the lower side wall portion in a state in which the upper container (20, 20A) is placed on the lower container (30, 30A, 30B, 30C, 30D), the lower container (30, 30A, 30B, 30C, 30D) has a shape with a plurality of corner portions in a plan view, and the foot portion (231, 231A) is arranged at a position corresponding to one of the corner portions, and the lower container (30, 30A, 30B, 30C, 30D) further includes a restriction portion (36, 37, 38) that is provided in the vicinity of the corner portion and prevents the foot portion (231, 231A) from entering to the inside of the lower container (30, 30A, 30B, 30C, 30D). a lower container (30, 30A, 30B, 30C, 30D) of which a top portion is open, the lower container (30, 30A, 30B, 30C, 30D) having a lower bottom portion and a lower side wall portion provided upright from a periphery of the lower bottom portion; and an upper container (20, 20A) of which a top portion is open, the upper container (20, 20A) being placed on the lower container (30, 30A, 30B, 30C, 30D), wherein an upper bottom portion in which a plurality of through holes is formed; an upper wall portion provided upright from a periphery of the upper bottom portion; and an extension wall portion extending downwardly from an outer face of the upper wall portion, and wherein a lower end portion of the extension wall portion is positioned below the upper bottom portion, characterised in that: a foot portion (231, 231A) is provided, which contacts with an installation surface on which the lower container (30, 30A, 30B, 30C, 30D) is installed in a state in which the upper container (20, 20A) is placed on the lower container (30, 30A, 30B, 30C, 30D), and a cutout portion is provided to expose the lower side wall portion in a state in which the upper container (20, 20A) is placed on the lower container (30, 30A, 30B, 30C, 30D), the lower container (30, 30A, 30B, 30C, 30D) has a shape with a plurality of corner portions in a plan view, and the foot portion (231, 231A) is arranged at a position corresponding to one of the corner portions, and the lower container (30, 30A, 30B, 30C, 30D) further includes a restriction portion (36, 37, 38) that is provided in the vicinity of the corner portion and prevents the foot portion (231, 231A) from entering to the inside of the lower container (30, 30A, 30B, 30C, 30D). a foot portion (231, 231A) is provided, which contacts with an installation surface on which the lower container (30, 30A, 30B, 30C, 30D) is installed in a state in which the upper container (20, 20A) is placed on the lower container (30, 30A, 30B, 30C, 30D), and a cutout portion is provided to expose the lower side wall portion in a state in which the upper container (20, 20A) is placed on the lower container (30, 30A, 30B, 30C, 30D), the lower container (30, 30A, 30B, 30C, 30D) has a shape with a plurality of corner portions in a plan view, and the foot portion (231, 231A) is arranged at a position corresponding to one of the corner portions, and the lower container (30, 30A, 30B, 30C, 30D) further includes a restriction portion (36, 37, 38) that is provided in the vicinity of the corner portion and prevents the foot portion (231, 231A) from entering to the inside of the lower container (30, 30A, 30B, 30C, 30D).