A catalyst for purifying exhaust gases includes a carrier substrate and a catalyst layer which is carried on the carrier substrate and contains a noble metal, a porous oxide and an additional oxide containing at least one selected from the group consisting of Ni, Bi, Sn, Fe, Co, Cu and Zn. Only a downstream section of the carrier substrate, which is located on a downstream side of an exhaust gas stream contains the additional oxide, whereas an upstream section of the carrier substrate does not contain the additional oxide. With this arrangement, in the upstream section of the carrier substrate, the noble metal and the additional oxide do not exist together so that the noble metal is not deteriorated with the additional oxide. As a result, in the upstream section, the purification performance as a three-way catalyst is favorably achieved, thereby restraining the emission of H2S while maintaining the three-way performance.