To provide an adsorbent which has a high removal performance of lower aliphatic aldehyde and a small deterioration with time of the removal performance of lower aliphatic aldehyde.

A porous body is impregnated with an ammonium salt of aminobenzenesulfonic acid. When the amount of the ammonium salt of aminobenzenesulfonic acid per 1g of the porous body is assumed to be A (g/porous body g) and a specific surface area of the porous body is S (m2/porous body g), A/S, i.e., the ratio of A to S, is in the range of 6×10-5≤A/S≤4×10-4.