PROBLEM TO BE SOLVED: To provide an odor suppression method and odor suppression composition for an odor-emitting material that can suppress the odor derived from hydrogen sulfide or methyl mercaptan or the like produced by the microorganism activity, for a long period of time and that has relatively low toxicity and that is inexpensive.SOLUTION: The odor emitted from an odor-emitting material is suppressed by adding, to the odor emitting-material, nitric acid or a salt thereof (nitric acid-based substance) and formic acid or a salt thereof (formic acid-based substance) in such a way that the concentration of the nitric acid-based substance in the odor-emitting material is 50 to 1000 mg/L in terms of nitric acid ion concentration and also the concentration of the formic acid-based substance in the odor-emitting material is 10 to 500 mg/L in terms of formic acid ion concentration.
