PURPOSE: To produce benzoquinone useful as an antioxidant, etc., economically, by the liquid-phase oxidation of phenol or an alkylphenol free from the substituent group at the p-position of the OH group with O2 gas in the presence of activated carbon or active alumina in the reaction liquid.

CONSTITUTION: p-Benzophenone is produced by the liquid-phase oxidation of phenol or an alkylphenol compound free from substituent group at the p-position of the OH group (e.g. phenol) with an oxygen-containing gas. The oxidation is carried out in a mixed solvent such as acetonitrile, methanol, etc. in the presence of a copper catalyst 0.2W2pts.wt. of powdery activated carbon or 0.2W2pts.wt. of active alumina (preferably powdery acidic alumina) based on 1pt.wt. of the phenolic compound. A high selectivity can be attained by using activated carbon when the starting compound is phenol or cresol, and using active alumina when it is o-t-butylphenol, etc.