The present invention aims to provide a pants type disposable diaper free from noticeable gathers formed on the innermost side of the crotch region. In the crotch region of the pants type disposable diaper, the bodily fluid-absorbent core is sandwiched between the liquid-permeable inner sheet and the liquid-impermeable outer sheet. Further inside the inner sheet, the innermost sheet is provided and this innermost sheet prevents the inner sheet from coming in contact with the wearer's skin. The innermost sheet is joined, in the regions extending in the vicinity of the ends thereof opposite in the front-back direction A, to at least one of the inner sheet and the outer sheet. The innermost sheet includes, in its region defined on the transverse center line P of the diaper, the tuck extending downward toward the inner sheet.