The present invention aims to achieve both a function of diffusing excretions or the like in a longitudinal direction of an absorber and maintenance of adhesion to a wearer in a direction orthogonal to the longitudinal direction. The absorber includes a top sheet (21), a back sheet (22) opposed to the top sheet (21), and an absorbent core (23) extending in a predetermined longitudinal direction between the top sheet (21), and the back sheet (22) and configured to absorb excretions or the like of the wearer. The absorbent core (23) has a plurality of opening portions (23a) each having a shape that opens toward the top sheet (21) and extends in the longitudinal direction and each arranged in the longitudinal direction. An interval (G1) in the longitudinal direction between two opening portions (23a) adjacent to each other among the plurality of opening portions (23a) is set to a dimension equal to or larger than a dimension (D1) in the longitudinal direction of each of the two adjacent opening portions (23a).