An exhaust system comprising an exhaust cleaning catalyst placed in an exhaust path from an internal combustion engine to clean exhaust expelled from the internal combustion engine, the catalyst comprising a porous substrate and a catalyst coating layer formed on the porous substrate, the catalyst coating layer having a carrier and a precious metal catalyst carried by the carrier, the precious metal catalyst being at least one species among Pt, Pd and Rh, the carrier comprising an OSC material that comprises at least CeO 2, and the catalyst coating layer being constituted in its thickness direction with multiple coating layers that includes at least two layers having different compositions, wherein the top coating layer forming the uppermost layer located at the outermost surface among the multiple coating layers has a top coating layer's upstream portion that includes at least 20 % of the full length of the top coating layer from its exhaust entrance-side end along the exhaust flow direction, and a top coating layer's downstream portion that includes at least 20 % of the full length of the top coating layer from its exhaust exit-side end along the exhaust flow direction the top coating layer's downstream portion comprises the CeO 2, the CeO 2 content in the top coating layer's upstream portion is less than the CeO 2 content in the top coating layer's downstream portion, and the bottom coating layer forming the lowest layer near the porous substrate among the multiple coating layers has a bottom coating layer's upstream portion that includes at least 20 % of the full length of the bottom coating layer from its exhaust entrance-side end along the exhaust flow direction, and a bottom coating layer's downstream portion that includes at least 20 % of the full length of the bottom coating layer from its exhaust exit-side end along the exhaust flow direction, the bottom coating layer's upstream portion comprises the CeO 2, and the CeO 2 content in the bottom coating layer's downstream portion is less than the CeO 2 content in the bottom coating layer's upstream portion. the catalyst comprising a porous substrate and a catalyst coating layer formed on the porous substrate, the catalyst coating layer having a carrier and a precious metal catalyst carried by the carrier, the precious metal catalyst being at least one species among Pt, Pd and Rh, the carrier comprising an OSC material that comprises at least CeO 2, and the catalyst coating layer being constituted in its thickness direction with multiple coating layers that includes at least two layers having different compositions, wherein the top coating layer forming the uppermost layer located at the outermost surface among the multiple coating layers has a top coating layer's upstream portion that includes at least 20 % of the full length of the top coating layer from its exhaust entrance-side end along the exhaust flow direction, and a top coating layer's downstream portion that includes at least 20 % of the full length of the top coating layer from its exhaust exit-side end along the exhaust flow direction a top coating layer's upstream portion that includes at least 20 % of the full length of the top coating layer from its exhaust entrance-side end along the exhaust flow direction, and a top coating layer's downstream portion that includes at least 20 % of the full length of the top coating layer from its exhaust exit-side end along the exhaust flow direction the top coating layer's downstream portion comprises the CeO 2, the CeO 2 content in the top coating layer's upstream portion is less than the CeO 2 content in the top coating layer's downstream portion, and the bottom coating layer forming the lowest layer near the porous substrate among the multiple coating layers has a bottom coating layer's upstream portion that includes at least 20 % of the full length of the bottom coating layer from its exhaust entrance-side end along the exhaust flow direction, and a bottom coating layer's downstream portion that includes at least 20 % of the full length of the bottom coating layer from its exhaust exit-side end along the exhaust flow direction, a bottom coating layer's upstream portion that includes at least 20 % of the full length of the bottom coating layer from its exhaust entrance-side end along the exhaust flow direction, and a bottom coating layer's downstream portion that includes at least 20 % of the full length of the bottom coating layer from its exhaust exit-side end along the exhaust flow direction, the bottom coating layer's upstream portion comprises the CeO 2, and the CeO 2 content in the bottom coating layer's downstream portion is less than the CeO 2 content in the bottom coating layer's upstream portion.