A static mixer for mixing a urea solution and engine exhaust gas, comprising: a) an external tube including one end portion connected to an exhaust manifold of a diesel engine, the other end portion connected to an SCR (Selective Catalytic Reduction), and a part with which a urea solution injection adaptor is provided; b) an internal tube installed inside the external tube so as to have a constant gap between at least a part of an outer wall surface and an inner wall surface of the external tube; c) a channel unit provided inside the internal tube, comprising a plurality of guiding channels in a longitudinal direction, and having an inlet portion (12, 12a, 12b) facing a lower end portion of the urea solution injector adaptor; d) wherein the inlet portion of the channel unit includes a first inclined portion having a predetermined angle with respect to a longitudinal direction of the channel unit, and a second inclined portion having a predetermined angle with respect to the first inclined portion, and is installed inside the internal tube; e) characterized in that the channel unit comprises a plurality of first channel plates arranged, in the longitudinal direction, with predetermined intervals therebetween, and a plurality of second channel plates inclined at a predetermined angle with respect to the plurality of first plates and disposed to cross the plurality of first plates with predetermined intervals therebetween; and f) in that a plurality of blades is provided at an end portion of an outlet side of at least one of the plurality of first and second channel plates (13, 14) so as to achieve a fine and even mixing behavior between the exhaust gas and the urea solution; g) in that the plurality of blades is inclinedly arranged in an opposite direction for each layer of the first and second channel plates (13, 14). a) an external tube including one end portion connected to an exhaust manifold of a diesel engine, the other end portion connected to an SCR (Selective Catalytic Reduction), and a part with which a urea solution injection adaptor is provided; b) an internal tube installed inside the external tube so as to have a constant gap between at least a part of an outer wall surface and an inner wall surface of the external tube; c) a channel unit provided inside the internal tube, comprising a plurality of guiding channels in a longitudinal direction, and having an inlet portion (12, 12a, 12b) facing a lower end portion of the urea solution injector adaptor; d) wherein the inlet portion of the channel unit includes a first inclined portion having a predetermined angle with respect to a longitudinal direction of the channel unit, and a second inclined portion having a predetermined angle with respect to the first inclined portion, and is installed inside the internal tube; e) characterized in that the channel unit comprises a plurality of first channel plates arranged, in the longitudinal direction, with predetermined intervals therebetween, and a plurality of second channel plates inclined at a predetermined angle with respect to the plurality of first plates and disposed to cross the plurality of first plates with predetermined intervals therebetween; and f) in that a plurality of blades is provided at an end portion of an outlet side of at least one of the plurality of first and second channel plates (13, 14) so as to achieve a fine and even mixing behavior between the exhaust gas and the urea solution; g) in that the plurality of blades is inclinedly arranged in an opposite direction for each layer of the first and second channel plates (13, 14).