To provide a disposable diaper for pets, that is easy to attach to pets. A disposable diaper for pets, having: a diaper longitudinal direction (Y), a diaper longitude-intersecting direction (X) being a direction intersecting the diaper longitudinal direction (Y)； a rear-side flap section (160)； a stomach-side flap section (150)； and a reference virtual straight line (100Y1) being a straight line in the longitudinal direction (Y) of the disposable diaper (10) for pets. The rear-side flap section (160) is configured such that the distance from the reference virtual straight line (100Y1) to an end section (160B) on the longitudinal intersection direction of the rear-side flap section (160) differs relative to the diaper longitudinal direction (Y).
