PROBLEM TO BE SOLVED: To provide an adsorbent which removes ammonia in air and does not produce hydrogen chloride in air and to provide an air purification filter and a method for manufacturing the filter. SOLUTION: The adsorbent is prepared by depositing on a carrier in a water- based medium containing silver ions and an ammonia fixing agent which fixes ammonia. The air purification filter has the above adsorbent on the surface of a supporting body. In the manufacture of the air purification filter, a material immersed in a water-based medium containing silver ions is used.