To provide an industrially very useful degradation method by which hardly degradable fluorinated carboxylic acids, salts thereof or precursors thereof can be degraded and made harmless safely under a mild condition.

The method for degrading the fluorinated carboxylic acids includes treating the fluorinated carboxylic acid, the salt thereof or the precursor thereof with hot water containing a peroxodisulfate ion in a sealed container. Preferably, the temperature of the hot water is 100-200C. The fluorinated carboxylic acid is represented by the general formula: RCOOH (R is an alkyl group containing at least one fluorine atom), and the alkyl group may contain a hydrogen atom, a halogen atom, an oxygen atom and an alkenyl residue besides the fluorine atom.