A disposable diaper for pets, having: a diaper longitudinal direction, a diaper longitude-intersecting direction being a direction interesting the diaper longitudinal direction； a rear-side flap section； a stomach-side flap section； and a reference virtual straight line being a straight line in the longitudinal direction of the disposable diaper for pets. The rear-side flap section is configured such that the distance from the reference virtual straight line to an end section on the longitudinal intersection direction of the rear-side flap section differs relative to the diaper longitudinal direction.
