In order to provide an exhaust gas purification device (1) having a construction whereby exhaust gas can flow into an exhaust gas inlet pipe (16) uniformly regardless of the shape of the pipe, the present invention is equipped with: a gas purification body (2) that purifies exhaust gas; a purification casing (60) housing the gas purification body (2); an exhaust gas inlet pipe (16) communicating with an exhaust gas inflow port (12) of the purification casing (60); and an exhaust gas outlet pipe (34) communicating with an exhaust gas outflow port of the purification casing (60). The exhaust gas inlet pipe (16) is attached to the purification casing (60) so as to cover the exhaust gas inflow port (12) and extend in the lengthwise direction of the purification casing (60). An exhaust gas introduction passage (200) is formed by the outer surface of the purification casing (60) and the pipe wall (201) inner surface of the exhaust gas inlet pipe (16). The portion (202) of pipe wall (201) which extends along the purification casing (60) is inclined so as to draw near to the outer surface of the purification casing (60) from the exhaust gas inlet side (16a) toward the exhaust gas outlet side (16b).