The present invention suppresses adhesion of a
urea aqueous solution to an interior wall of an
exhaust pipe and reduces flow resistance inside the
exhaust pipe, in a
urea aqueous solution mixing device. This
urea aqueous solution mixing device is provided with an
exhaust pipe (4B), an
injector (5), a mixing
pipe (6), an interior
pipe (7), and a flow unit (20). The exhaust
pipe (4B) has an
elbow part (10) with a curved section, and a straight part (11). The
injector (5) injects the urea aqueous solution, and is provided in the
elbow part (10). The mixing pipe (6) is positioned so as to cover the area around the urea aqueous solution injected by the
injector (5), and has an exit part formed between the interior walls of the exhaust pipe (4B) with an interval interposed therebetween, and a plurality of openings (6a) formed in the outer-
peripheral surface thereof. The interior pipe (7) allows
exhaust gas to flow through the interior and outer-
peripheral sections thereof, and is positioned in the straight part (11) of the exhaust pipe (4B). The flow unit (20) guides
exhaust gas into the interior pipe (7), and is formed between the exit part of the mixing pipe (6) and the interior walls of the exhaust pipe (4B).