The present invention provides a disposable pants-type diaper including on a crotch region thereof a separator adapted to prevent feces from coming in contact with the wearer's skin. A basic structure has the crotch region, which is provided with a folded sheet piece attached thereto so as to form the separator. The folded sheet piece is obtained by folding back the sheet piece along a first transverse center line thereof to define a first half and a second half placed upon each other and bonding end edges of these two halves to each other at responsive middles of these end edges in a transverse direction. With the first transverse center line brought close to a second transverse center line, the folded sheet piece is placed upon the crotch region and the lateral edges of the first half are bonded to the crotch region while a region of the first half defined by the lateral edges is kept to be spaced from the crotch region. Then, the basic structure is folded back along the second transverse center line and the inner surface of the basic structure is bonded to the outer surface of the lateral edges of the second half while a region of the second half defined between the lateral edges is kept to be spaced from the crotch region. Of the basic structure folded back in this manner, the front and rear waist regions are bonded along the lateral edges to make the basic structure in a pants-shape.