An absorbent article having a longitudinal direction, a lateral direction, and a thickness direction, the absorbent article comprising: an absorbent core including superabsorbent polymer particles, wherein the absorbent core has a non-skin facing surface, and a skin facing surface, and is formed of a first layer on a non-skin facing surface side, and a second layer on a skin facing surface side, the first layer includes: a plurality of groove portions that includes a plurality of main groove portions extending in the longitudinal direction and penetrating the first layer in the thickness direction, and a plurality of base portions that extend in the longitudinal direction, each of the plurality of main groove portions and each of the plurality of base portions are arranged alternately in the lateral direction, each of the plurality of base portions is formed of: a base inner side portion adjacent to the non-skin facing surface side of the second layer, and a base outer side portion adjacent to the non-skin facing surface side of the base inner side portion, and an average density of the superabsorbent polymer particles contained in the base outer side portion is lower than an average density of the superabsorbent polymer particles contained in the base inner side portion wherein the second layer includes: a plurality of main groove portion corresponding portions and a plurality of base corresponding portions arranged at positions overlapping with the plurality of main groove portions and the plurality of base portions in the thickness direction, respectively, and charactertised in that: both an average density of the superabsorbent polymer particles contained in each of the plurality of base portions and an average density of the superabsorbent polymer particles contained in each of the plurality of main groove portion corresponding portions are lower than an average density of the superabsorbent polymer particles contained in each of the plurality of base corresponding portions. an absorbent core including superabsorbent polymer particles, wherein the absorbent core has a non-skin facing surface, and a skin facing surface, and is formed of a first layer on a non-skin facing surface side, and a second layer on a skin facing surface side, the first layer includes: a plurality of groove portions that includes a plurality of main groove portions extending in the longitudinal direction and penetrating the first layer in the thickness direction, and a plurality of base portions that extend in the longitudinal direction, a plurality of groove portions that includes a plurality of main groove portions extending in the longitudinal direction and penetrating the first layer in the thickness direction, and a plurality of base portions that extend in the longitudinal direction, each of the plurality of main groove portions and each of the plurality of base portions are arranged alternately in the lateral direction, each of the plurality of base portions is formed of: a base inner side portion adjacent to the non-skin facing surface side of the second layer, and a base outer side portion adjacent to the non-skin facing surface side of the base inner side portion, and a base inner side portion adjacent to the non-skin facing surface side of the second layer, and a base outer side portion adjacent to the non-skin facing surface side of the base inner side portion, and an average density of the superabsorbent polymer particles contained in the base outer side portion is lower than an average density of the superabsorbent polymer particles contained in the base inner side portion wherein the second layer includes: a plurality of main groove portion corresponding portions and a plurality of base corresponding portions arranged at positions overlapping with the plurality of main groove portions and the plurality of base portions in the thickness direction, respectively, and charactertised in that: both an average density of the superabsorbent polymer particles contained in each of the plurality of base portions and an average density of the superabsorbent polymer particles contained in each of the plurality of main groove portion corresponding portions are lower than an average density of the superabsorbent polymer particles contained in each of the plurality of base corresponding portions.