A disposable diaper for pets having a shortest straight line point being further on a stomach-side waist area side than a diaper center point, and comprising: a rear-side waist area； a stomach-side waist area； a crotch area； a flap section provided in the stomach-side waist area and having an end section in the rear-side direction； a diaper longitudinal direction center line； the diaper center point； a tail insertion opening； an absorbent core； an attachment section arranged in the flap section； an attachment section intermediate point； an attachment area that receives the attachment section； and the shortest straight line point being a point on the diaper longitudinal direction center line at the shortest direct distance, via a rear-side end section of the flap section in a straight line from the attachment section center point to the diaper longitudinal direction center line.
