The utility model discloses a confluence device which is used for solving the problem that the viscosity of polymer solution is lost in the course of injecting water to mix with the polymer solution. The confluence device comprises a first pipeline and a second pipeline, wherein the first pipeline comprises a liquid inlet end and a liquid outlet end; the liquid inlet end is used for inputting first liquid; the liquid outlet end is used for connection with a mixed liquid output pipe; the second pipeline comprises a liquid inlet and a liquid outlet; the liquid inlet is used for inputting second liquid; the liquid outlet stretches into the first pipeline through a connection part between the second pipeline and the first pipeline; the direction of the liquid outlet of the second pipeline is parallel with the axis direction located at the connection part of the second pipeline and the first pipeline, and faces the liquid outlet end of the first pipeline; the first liquid is either injected water or the polymer solution; the second liquid is either the injected water or the polymer solution, and is different from the first liquid. By adopting the confluence device, the viscosity loss, caused in the course of mixing the injected water and the polymer solution, of the polymer solution can be reduced.