Provided is an unfolding-type disposable diaper wherein: a diaper body portion, which has a vertical direction, horizontal direction, and thickness direction that are orthogonal to each other, has, in a row in the vertical direction, a first waist portion, a crotch portion, and a second waist portion； the first waist portion and the second waist portion are connected by engaging a fastening tape engagement portion, which is provided so as to protrude to the outside in the horizontal direction from the second waist portion, with the first waist portion； and one waist opening portion and a pair of crotch opening portions are formed. A cutoff line for cutting at least the fastening tape engagement portion off from the second waist portion is provided. A mark that indicates the location of at least a portion of the cutoff line is provided so as to correspond to said portion.
