Disclosed is a good and simple method for decomposing and detoxifying a hardly decomposable fluorine-containing organic compound. Specifically, a fluorine-containing organic compound is decomposed by bringing an aqueous solution of the fluorine-containing organic compound into contact with a catalyst containing a metal oxide. The metal oxide may preferably be an oxide of at least one metal selected from the group consisting of Ni, Pd, Cu, Mn, Fe and Co, and more preferably be nickel oxide. The contact temperature is preferably be within the range of 0-100 DEG C. Preferably, the fluorine-containing organic compound to be decomposed is an organic fluorocarboxylic acid, an organic fluorosulfonic acid or a salt of one of organic fluorocarboxylic acids and organic fluorosulfonic acids, which is used as a surfactant or an surface treatment agent.