To provide a new oxidation catalyst.

The oxidation catalyst is composed of organic metal salt and an organic acid having 4.57 acidity constant pKa. The organic metal salt is preferably Cu(OAc)2, Co(OAc)2, Ni(OAc)2, Mn(OAc)2, Zn(OAc)2 or Pd(OAc)2. The organic acid is preferably tBuCOOH, 1-AdamantylCOOH, c-C6H11COOH or C2H5COOH. Alernatively, the oxidation catalyst is composed of an inorganic metal compound and the organic acid having 4.57 acidity constant pKa. The inorganic metal compound is preferably Cu2O, CuO or CuCl. The organic acid is preferably tBuCOOH, 1-AdamantylCOOH, c-C6H11COOH or C2H5COOH. Alternatively, the oxidation catalyst consists of salt of the organic acid having 4.57 acidity constant pKa. The salt is preferably Cu[OC(O)tBU]2 or Co[OC(O)tBU]2.