An oxidation catalyst according to the present invention is prepared, for example, by heat processing a gold compound at 150° C. to 80° C., yielding ultrafine gold particles, which are then mixed with a palladium compound and a compound containing at least one element selected from the group consisting of alkaline metals and the elements of Groups IIA, IIIA, VIA, IIB, VB, and VIII of the Periodic Table. By an oxidation reaction between a benzyl compound such as p-xylene and a carboxylic acid such as acetic acid in the presence of oxygen and the oxidation catalyst prepared as above, a benzyl ester such as p-methylbenzyl acetate or p-xylylene diacetate can be produced. Consequently, it is possible to provide an oxidation catalyst suitable for use in industrially producing the foregoing benzyl esters, a method of preparing the foregoing oxidation catalyst, and a method of producing the foregoing benzyl esters efficiently and at low cost.