An exhaust purification device has a catalytic converter provided with: an outer cylinder welded at the upstream end portion to an exhaust gas inlet of an inlet-side flange and welded at the downstream end portion to an exhaust gas outlet of the outlet-side flange. An inner cylinder has an upstream end portion held by the upstream side portion of the outer cylinder with no gap and has a downstream end portion disposed at the downstream side of the outer cylinder with a gap, the inner cylinder housing a catalyst support. An opening end is formed at the downstream end portion of the inner cylinder with a gap with respect to the outer cylinder, and a gas layer is formed by the exhaust gas having entered from the exhaust gas inlet and convected to an upstream side between the outer cylinder and the inner cylinder.