Fluid adding device and water purifier

The utility model discloses a fluid adding device and a water purifier. The fluid adding device comprises a containing cavity, a resistance element and a liquid outlet pipeline. A liquid inlet and a liquid outlet are formed in the containing cavity, the liquid outlet of the containing cavity is connected with the liquid inlet end of the resistance element, and the liquid outlet pipeline is connected with the liquid outlet end of the resistance element; a flexible bag is arranged in the containing cavity, the liquid outlet end of the flexible bag communicates with the liquid outlet pipeline through an output pipeline, and a first one-way valve is arranged on the output pipeline. The larger the flow of the liquid flowing through the resistance element is, the larger the upstream and downstream pressure difference generated by the resistance element is. The fluid adding device can achieve automatic adding of fluid, does not need to be provided with an additional driving unit, and has the advantages of being simp