PROBLEM TO BE SOLVED: To provide a treatment agent for an absorbent article, and a method of treating an absorbent article, which enable an absorbent article to be treated in a simple manner.SOLUTION: A treatment agent for an absorbent article includes an acidic solid substance, at least one alkaline solid substance selected from the group consisting of sodium bicarbonate, hydrated lime and limestone, a carboxyvinyl polymer, zeolite, and a zinc oxide.