Absorber

An absorber comprising

• an absorber core containing water-absorbent resin particles,
• wherein a diffusion area change ratio measured in the order of the following (1) to (5) is 0.80 to 1.0,
• (1) an absorbent article is produced by disposing, on an upper surface of the absorber, an air-through type polyethylene porous liquid permeable sheet having a basis weight of 22 g/m2 and having the same area as that of the absorber,
• (2) the absorbent article is placed horizontally, a cylinder having an opening with an inner diameter of 3 cm is placed on a center of the absorbent article, 80 ml of artificial urine is injected into the cylinder at one time, and the cylinder is removed,
• (3) an area S1 of a surface of the absorber on which the artificial urine is diffused is measured 20 minutes after the artificial urine injection,
• (4) a second artificial urine injection is performed in the same manner as in (2) 30 minutes after the first artificial urine injection, and a total area S2 of the surface of the absorber on which the artificial urine is diffused is measured 20 minutes after the second artificial urine injection, and
• (5) the operation of (4) is repeated twice more to measure a diffusion area S3 at the time of a third injection and a diffusion area S4 at the time of a fourth injection,
• diffusion area change ratio=(S1+S2)/(S3+S4).