An exhaust purification device having a catalytic converter into which exhaust gas (G) flows, the catalytic converter comprising: an inner cylinder accommodating therein a catalyst support for purifying the exhaust gas (G); and an outer cylinder having a large-diameter cylindrical base portion disposed with a predetermined gap (T) to an outer periphery of the inner cylinder so as to surround the outer periphery of the inner cylinder , said outer cylinder having an upstream end portion serving as an inlet of the exhaust gas and a downstream end portion serving as an outlet of the exhaust gas; characterized in that the inner cylinder has an upstream end portion held with no gap via a heat-insulating member having an elastic force to an upstream end portion in a flow direction of the exhaust gas (G) of the large-diameter cylindrical base portion , and has a downstream end portion disposed with the predetermined gap (T) on a downstream side of the outer cylinder ; the exhaust gas (G) having passed through the catalyst support flows into the gap (T) between the inner cylinder and the large-diameter cylindrical base portion through an opening end provided between a downstream side of the inner cylinder and a downstream end portion of the large-diameter cylindrical base portion in the flow direction of the exhaust gas (G); and a gas layer is formed by the exhaust gas (G) having flowed into an interior of the inner cylinder from the upstream end portion of the outer cylinder, having been discharged from the downstream end portion of the inner cylinder , and convected from the predetermined gap (T) to an upstream side between the outer cylinder and the inner cylinder . an inner cylinder accommodating therein a catalyst support for purifying the exhaust gas (G); and an outer cylinder having a large-diameter cylindrical base portion disposed with a predetermined gap (T) to an outer periphery of the inner cylinder so as to surround the outer periphery of the inner cylinder , said outer cylinder having an upstream end portion serving as an inlet of the exhaust gas and a downstream end portion serving as an outlet of the exhaust gas; characterized in that the inner cylinder has an upstream end portion held with no gap via a heat-insulating member having an elastic force to an upstream end portion in a flow direction of the exhaust gas (G) of the large-diameter cylindrical base portion , and has a downstream end portion disposed with the predetermined gap (T) on a downstream side of the outer cylinder ; the exhaust gas (G) having passed through the catalyst support flows into the gap (T) between the inner cylinder and the large-diameter cylindrical base portion through an opening end provided between a downstream side of the inner cylinder and a downstream end portion of the large-diameter cylindrical base portion in the flow direction of the exhaust gas (G); and a gas layer is formed by the exhaust gas (G) having flowed into an interior of the inner cylinder from the upstream end portion of the outer cylinder, having been discharged from the downstream end portion of the inner cylinder , and convected from the predetermined gap (T) to an upstream side between the outer cylinder and the inner cylinder . <EOS>