To produce p-benzoquinones in a good reaction yield by preparing an oxidation catalyst from the copper salt of a mixed acid consisting of an alkanesulfonic acid and an aliphatic carboxylic acid and amines or oximes.

The oxidation catalyst suitable for use in the production of p-benzoquinones is obtained using the copper salt of a mixed acid consisting of an alkanesulfonic acid and an aliphatic carboxylic acid and amines or oximes. Phenols of formula I are oxidized with molecular oxygen in the presence of the oxidation catalyst to produce the objective p-benzoquinones of formula II. In the formulae I and II, X is H or hydroxyl and R1-R4 are each H, alkyl, alkoxy, aryl, aryloxy, halogen or the like. Gaseous oxygen or an oxygen- containing gas such as air may be used as the molecular oxygen.