To provide an oxidation catalyst for cleaning an exhaust gas which effectively oxidizes unburned hydrocarbons in the exhaust gas discharged from an internal engine and making a catalyst temperature rise by atomizing with a little fuel, and an exhaust gas cleaning system.

The oxidation catalyst for cleaning an exhaust gas is formed by coating an integrated structure type carrier with a catalyst layer exhibiting a catalytic activity to the oxidation reaction of hydrocarbons. The catalyst layer uses active alumina carrying platinum and/or palladium as a main component and contains β type zeolite ion exchanged with cerium. The exhaust gas cleaning system having the oxidation catalyst for cleaning the exhaust gas disposed in an exhaust gas flow passage containing the unburned hydrocarbons makes the exhaust gas flow to the catalyst to oxidize the unburned hydrocarbons to heat the exhasut gas by oxidation heat generated at that time.