Provided is an oxidation catalyst for diesel engines, which enables reduction of the production cost, while maintaining the performance of an oxidation catalyst. An oxidation catalyst for diesel engines, which is configured of a plurality of catalyst layers containing Pt and/or Pd. This oxidation catalyst for diesel engines is divided into an upstream-side catalyst layer 5 and a downstream-side inner catalyst layer 6 in the flow direction of the exhaust gas, and a downstream-side outer catalyst layer 7 is additionally formed so as to cover the surface of the downstream-side inner catalyst layer 6. The upstream-side catalyst layer 5 and the downstream-side inner catalyst layer 6 contain Pd, and the downstream-side outer catalyst layer 7 contains Pt. The amounts of Pt and Pd contained in the upstream-side catalyst layer 5 and the amounts of Pt and Pd contained in the downstream-side inner catalyst layer 6 are constantly set to certain values, while the amount of Pt contained in the downstream-side outer catalyst layer 7 is set to a value which enables the oxidation efficiency to be at a predetermined value or higher.