TO PROVIDE A DISPOSABLE DIAPER FOR PETS THAT FITS WELL AROUND THE WAIST OF THE PET. A DISPOSABLE DIAPER FOR PETS HAVING: A REAR 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 (100A) IN A 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 RECEIVES THE ATTACHMENT SECTION (300) AND AN EXPANDABLE/CONTRACTIBLE ELASTIC MEMBER (600) FOR A LEAKAGE PREVENTION SHEET ARRANGED IN AN EXTENDED STATE IN THE LEAKAGE PREVENTION SHEET (800). THE EXPANDABLE/CONTRACTIBLE ELASTIC MEMBER (600) FOR THE LEAKAGE PREVENTION SHEET IS ARRANGED IN A PRESCRIBED AREA IN THE DIAPER LONGITUDINAL DIRECTION BETWEEN THE ABSORBENT CORE (200) AND THE END SECTION (100A) IN THE DIAPER LONGITUDE INTERSECTING DIRECTION. A STANDING UP SECTION (700) IN WHICH THE END SECTION IN THE DIAPER LONGITUDINAL DIRECTION STANDS UP IS FORMED AS A RESULT OF THE CONTRACTION OF THE EXPANDABLE/CONTRACTIBLE ELASTIC MEMBER (600) FOR THE LEAKAGE PREVENTION SHEET.
