PROBLEM TO BE SOLVED: To provide an underpants type wearing article which has an appearance like underwear even though it has a side seal part and has excellent touch in the side seal part.SOLUTION: A diaper 50B in this invention includes an exterior body 3 forming an outer surface, and in the diaper, a pair of side seal parts 4, 4, a waist opening part 8, and a pair of leg opening parts 9, 9 are formed by connecting both side edge parts of the exterior body 3 in a front body F to both side edge parts of the exterior body 3 in a rear body R. The side seal part 4 has a sealed edge part 41 in which an edge part of the exterior body in the front body and an edge part of the exterior body in the rear body are joined together at a continuous linear fusion part 40 extending in a longitudinal direction of the side seal part. In the fusion part 40, a thickness T, in a cross section orthogonal to a direction in which the side seal part extends, is equal to or smaller than a total thickness (Tb+Tb) of the exterior body on the side of the front body F and the exterior body on the side of the rear body R and is greater than at least one of the thicknesses (Ta or Tb) of the exterior body on the side of the front body F and the exterior body on the side of the rear body R.
