The invention provides a paper diaper for a pet. Even a large dog can wear the paper diaper easily, excrement is not leaked, and the wearing state can be changed easily in dependence on the health condition of the pet. The paper diaper (100) for the pet comprises a flake-like water absorption body (130) and a main body part (110). When being looked down, the water absorption body (130) is approximately rectangular. The main body part (110) maintains the water absorption body (130) along the direction being from the exterior to the interior, and is formed by at least two layers, and is approximately rectangular. A part, of the main body part, used for cylindrically covering the waist of the pet is arranged at two end sides of a short edge of the approximate rectangle when the paper diaper is worn, and therefore a waist back part (112) and a waist abdomen part (114) are formed. The main body part (110) is provided with a U-shaped hole part (150) (passing-through part) used for the tail of the pet to pass through when the paper diaper is worn by the pet, and the hole part (150) is arranged next to the short edge of the water absorption body (130). The position being next to the hole part (150) at a non-hygroscopic surface side of the main body part (110) is provided with two adjusting belts (160) used for pulling the water absorption body (130) to the back side when the paper diaper is worn by the pet.
