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 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 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 . 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 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 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 . <EOS>