An apparatus includes a first rotary disc, a plurality of folding plates mounted on a peripheral zone of the first rotary disc, a plurality of positive motion cams mounted on the peripheral zone of the first rotary disc so as to be interposed between the first rotary disc and the folding plates, a second rotary disc located on a side opposite to the first rotary disc and a plurality of auxiliary plates mounted on a peripheral zone of the second rotary disc. The folding plates and the auxiliary plates synchronously move into a contiguous diaper structure and simultaneously the guide arms move into a clearance between the guide blades so that opposite lateral zones of a crotch region may be held between the guide arms and the guide blades and thereby the crotch region may be tucked into the contiguous diaper structure.