PROBLEM TO BE SOLVED: To provide: a diketone action inhibitor capable of effectively suppressing diketone compound action and a body odor-suppressing agent capable of effectively suppressing body odor, particularly acid odor in the oxter part and fatty smell in the head.SOLUTION: A diketone action inhibitor suppressing diketone compound action, is represented by general formula (I) :R-(CO)-(CO)-R(I) (where, Rand Rare each independently an alkyl group having a carbon number 1 to 4). The diketone action inhibitor contains at least one kind of extract selected from a group consisting of Filipendula multijuga extract, Himalayan Raspberry extract, linden extract and rose extract, and a body odor-suppressing agent contains the diketone action inhibitor.