A process for producing a diazomethane derivative by oxidizing a hydrazone derivative in a two-phase system containing: a) an aqueous solution of a mixture of a caustic alkali and an alkali metal hypochlorite in respective concentrations of 4-14 w/w % and 3-10 w/w % based on the total weight of the solution; b) a hydrophobic organic solvent; c) an inorganic iodine compound, and d) a phase-transfer catalyst.
