PROBLEM TO BE SOLVED: To provide an underpants type absorbent article allowing easy longitudinal tearing of a side seal part by eliminating the variation of a lateral breaking position when tearing the side seal part.SOLUTION: An underpants type disposable diaper 1 includes a belly side part A and a back side part B, and includes a pair of side seal parts S formed by joining both edge parts of the belly side part A and both edge parts of the back side part B in a palm jointing state. The side seal part S has a plurality of seal patterns 5 intermittently formed in the long direction of the diaper 1. Each of the plurality of seal patterns 5 has one side 51 extending in the diaper long direction, and when connecting line segments P, P connecting the one sides 51 of the adjacent seal patterns 5 at a minimum distance, one straight line P is formed. The seal patterns 5 are present on both the right and left sides of the straight line P.
