This diaper (50B) is a disposable pants-type diaper which is provided with an outer body (3) forming the outer surface, and in which 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 joining the right and left edges of the outer body (3) in the front body section (F) and the right and left edges of the outer body (3) in the rear body section (R), wherein the side seal parts (4) form the edge part (3F) of the outer body in the front body section and the edge part (3R) of the outer body in the rear body section, seal edge parts (41) are continuously formed along the entire length of the side seal parts, and the fusion strength varies along the lengthwise direction thereof.
