Abstract: An exhaust gas purification device (1) including: a spray nozzle (2) provided in an exhaust pipe of an engine (18); a mixer (11) provided downstream of the spray nozzle in a flow direction of exhaust gas; and a catalyst reactor (12) provided downstream of the mixer. The exhaust gas purification device is configured to spray a reducing agent from the urea water spray nozzle to the exhaust gas from the engine, to mix the reducing agent with the exhaust gas in the mixer, and to reduce nitrogen oxides in the exhaust gas using the catalyst reactor. The mixer includes a cylindrical body (21) and a plurality of fins (22) arranged in the cylindrical body radially outward with respect to the axis of the cylindrical body. The upstream portion of each fin is shaped to provide a cutoff portion (221).