A disposable diaper for pets, in which a fixed section in an attachment section overlaps with an expanding/contracting elastic member for the waist, said disposable diaper for pets having: a rear-side waist area a stomach-side waist area a crotch area both end sections in the diaper longitudinal direction both end sections in the diaper longitude-intersecting direction a tail insertion opening an absorbent core an area not having the absorbent core arranged therein a flap section provided in the stomach-side waist area and having an end section in the rear-side direction an attachment section having the fixed section arranged in the flap section and a free section extending from the flap section the expanding/contracting elastic member for the waist and an attachment area that receives the attachment section.
