Provided is an underwear type diaper that fits the shape of an infant under half a year old and that is such that gather marks are not easily imparted. The underwear type diaper (10) is provided with: a front waist region (18) and back waist region (19) that have a horizontal direction (X) and a vertical direction (Y) that are perpendicular to each other a crotch region (13) joined to the front and back waist regions and a leg cuff (40) that extends along both edges of the crotch region (13). Each of a front and a back waist panel is segmented into a first extending/contracting region (26) and a second extending/contracting region (27) the ratio of the dimensions in the vertical direction of the first extending/contracting region and the second extending/contracting region is in the range of 1:1.6 2.2 the elongation rate of the waist elastic body (30) attached to the first extending/contracting region is lower than the elongation rate of the waist elastic body attached to the second extending/contracting region and the elongation rate of the waist elastic body attached to the second extending/contracting region is lower than the elongation rate of a second leg elastic body (42).
