A disposable diaper for pets, in which part of a crotch area stands up as a result of the contraction of an expanding/contracting elastic member, and a standing-up section is formed, said disposable diaper for pets having: a rear-side waist area; a stomach-side waist area; the 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 attachment section provided in the stomach-side waist area; an attachment area that receives the attachment section; and the expanding/contracting elastic member arranged the diaper longitudinal direction.