An exhaust-gas purification device includes an injection nozzle provided inside an exhaust pipe and a catalyst reactor provided on a downstream side of the injection nozzle, and is configured to inject urea water from the urea water injection nozzle into exhaust gas and to reduce nitrogen oxide in the exhaust gas by a NOx catalyst contained in the catalyst reactor, where the injection nozzle is disposed to inject the urea water toward the downstream side of the flow direction of the exhaust gas, and a mixer is connected to an upstream end of the catalyst reactor, the mixer having a plurality of plate members radially disposed around the axial center of the exhaust pipe, the plate members each being formed in such a way that angles of plate surfaces of the plate member to the flow direction are different values on the upstream side and the downstream side.