An exhaust treatment device that treats an exhaust gas from an internal combustion engine, the exhaust treatment device comprising: a cylindrical shell into which the exhaust gas is introduced; and a flow channel pipe (16,18) inserted in such a manner as to penetrate through the cylindrical shell, wherein the exhaust treatment device is configured such that one end of the flow channel pipe (16,18) is connected to an exhaust-gas flow path of the internal combustion engine and the exhaust gas flowing through the exhaust-gas flow path is introduced into the cylindrical shell via the flow channel pipe (16,18), wherein a pair of through holes (22,36, 24,38), in which the flow channel pipe (16,18) is disposed, are provided in a pipe wall of the cylindrical shell, diameters of the pair of through holes (22,36, 24,38) being slightly larger than an outer diameter of the flow channel pipe (16,18), wherein a lid member (30,40) configured to occlude one of the through holes (24,38) is welded to an other end of the flow channel pipe (16,18) so as to occlude an opening in the other end of the flow channel pipe (16,18), wherein the lid member (30,40) is welded to the pipe wall of the cylindrical shell so that the one of the through holes (24, 38) is occluded by the lid member (30,40), wherein a clearance between one of the through holes (24,38) and the flow channel pipe (16,18) is occluded by the lid member (30,40) when the lid member (30,40) is disposed, wherein a cylindrical portion (20, 34) is provided in the other of the through holes (22,36), the cylindrical portion (20, 34) being a part of the pipe wall of the cylindrical shell, and characterised in that the flow channel pipe (16, 18) is arranged in such a manner as to obliquely cross the cylindrical shell, and wherein the central axis of the flow channel pipe (16, 18) deviates from the center of the cylindrical shell, and a cutting surface of the other end of the flow channel pipe (16, 18) is inclined with respect to the central axis along a length direction of the flow channel pipe (16, 18). a cylindrical shell into which the exhaust gas is introduced; and a flow channel pipe (16,18) inserted in such a manner as to penetrate through the cylindrical shell, wherein the exhaust treatment device is configured such that one end of the flow channel pipe (16,18) is connected to an exhaust-gas flow path of the internal combustion engine and the exhaust gas flowing through the exhaust-gas flow path is introduced into the cylindrical shell via the flow channel pipe (16,18), wherein a pair of through holes (22,36, 24,38), in which the flow channel pipe (16,18) is disposed, are provided in a pipe wall of the cylindrical shell, diameters of the pair of through holes (22,36, 24,38) being slightly larger than an outer diameter of the flow channel pipe (16,18), wherein a lid member (30,40) configured to occlude one of the through holes (24,38) is welded to an other end of the flow channel pipe (16,18) so as to occlude an opening in the other end of the flow channel pipe (16,18), wherein the lid member (30,40) is welded to the pipe wall of the cylindrical shell so that the one of the through holes (24, 38) is occluded by the lid member (30,40), wherein a clearance between one of the through holes (24,38) and the flow channel pipe (16,18) is occluded by the lid member (30,40) when the lid member (30,40) is disposed, wherein a cylindrical portion (20, 34) is provided in the other of the through holes (22,36), the cylindrical portion (20, 34) being a part of the pipe wall of the cylindrical shell, and characterised in that the flow channel pipe (16, 18) is arranged in such a manner as to obliquely cross the cylindrical shell, and wherein the central axis of the flow channel pipe (16, 18) deviates from the center of the cylindrical shell, and a cutting surface of the other end of the flow channel pipe (16, 18) is inclined with respect to the central axis along a length direction of the flow channel pipe (16, 18).