TO PROVIDE A DISPOSABLE DIAPER FOR PETS THAT FITS WELL AROUND THE WAIST OF THE PET. [SOLUTION] A DISPOSABLE DIAPER FOR PETS COMPRISING: A BACK SIDE WAIST AREA (130) A STOMACH SIDE WAIST AREA (110) A CROTCH AREA (120) BOTH END SECTIONS (130A 110A) IN THE DIAPER LONGITUDINAL DIRECTION BOTH END SECTIONS (120A) IN THE DIAPER LONGITUDE INTERSECTING DIRECTION A TAIL INSERTION OPENING (190) AN ABSORBENT CORE (200) AN AREA (170) NOT HAVING THE ABSORBENT CORE ARRANGED THEREIN AN ATTACHMENT SECTION (300) PROVIDED IN THE STOMACH SIDE WAIST AREA (110) AN ATTACHMENT AREA (900) THAT ACCEPTS THE ATTACHMENT SECTION (300) AN EXPANDABLE/CONTRACTIBLE ELASTIC MEMBER (400) FOR LEGS ARRANGED IN AN EXTENDED STATE IN A PRESCRIBED AREA IN THE DIAPER LONGITUDINAL DIRECTION BETWEEN THE ABSORBENT CORE (200) AND AN END SECTION (100A) IN THE DIAPER LONGITUDE INTERSECTING DIRECTION A LEG GATHER (410) FORMED BY THE CONTRACTION OF THE EXPANDABLE/CONTRACTIBLE ELASTIC MEMBER (400) FOR LEGS AN EXPANDABLE/CONTRACTIBLE ELASTIC MEMBER (500) FOR THE WAIST ARRANGED IN AN EXTENDED STATE IN THE AREA NOT HAVING THE ABSORBENT CORE ARRANGED THEREIN IN THE DIAPER LONGITUDE INTERSECTING DIRECTION AND A CONTRACTION FORCE INTERSECTING AREA (180) IN WHICH THE CONTRACTING FORCE OF THE EXPANDABLE/CONTRACTIBLE ELASTIC MEMBER (400) FOR LEGS AND THE EXPANSION/CONTRACTION FORCE OF THE EXPANDABLE/CONTRACTIBLE ELASTIC MEMBER (500) FOR THE WAIST INTERSECT.
