The present invention provides a method for oxidizing a hydrocarbon, an alcohol or an aldehyde, which comprises: oxidizing a hydrocarbon, an alcohol or an aldehyde to an alcohol, an aldehyde, a carboxylic acid or a carboxylate ester corresponding thereto, in a liquid phase having: a region in which oxygen is substantially present; and a region in which oxygen is substantially absent, in the presence of a catalyst containing a palladium, wherein the region in which oxygen is substantially absent is 0.1 to 10% by volume with respect to a total of the region in which oxygen is substantially present and the region in which oxygen is substantially absent.