To obtain the subject compound useful as an intermediate for vitamin Ks in high conversion and selectivity at low installation cost.

This compound 2-methyl-1,4-benzoquinone, is obtained by oxidation of m-cresol by molecular oxygen in a water-acetonitrile mixed solvent in the presence of a catalyst consisting of a combination of a copper halide (e.g. cupric chloride) with a manganese halide (e.g. manganous chloride) under an oxygen partial pressure of 2-20kg/cm2 at 50-100°C. The mixed solvent contain pref. 20-60wt.% of water. The volume ratio of the mixed solvent to m-cresol is pref. 3-20. For the catalyst, the molar ratio of the copper halide to manganese halide is pref. (1:0.5) to (1:1.5), and the amount of the catalyst to be used is pref. 0.05-0.5mol based on the m-cresol.