A disposable diaper for pets, having: a rear-side waist area a stomach-side waist area a crotch area a rear-side flap section a stomach-side flap section and a tail insertion opening. At least either the rear-side flap section or the stomach-side flap section have an identification area. A determination can be made that there is a problem with the state of the rear-side flap section, on the basis of visual inspection information about the identification area, said visual inspection being performed externally on the disposable diaper for pets.
