A process of producing an aliphatic aldehyde-acid (e.g., adipaldehyde-acid) and/or an aliphatic dicarboxylic acid (e.g., adipic acid) comprising oxidizing a cyclic ketone (e.g., cyclohexanone) with molecular oxygen in the presence of a fixed catalyst which comprises a composite of a carrier and at least one metal element belonging to the groups 4 to 11 of the Periodic Table supported on the carrier and has an acid amount of 0.06 mmol/g or more per unit weight of the carrier.