A spout assembly includes a main body coupled on an opening of a container, a lip portion formed on the main body, having an operating portion and a coupling portion, a spouting guide installed in the operation portion of the lip portion, being vertically movable, and an upper cap coupled on the coupling portion to provide seal to the main body. The lip portion is provided with a seal projection having a side exhaust hole, the seal projection sealing a lower end of the spouting guide, and the spouting guide.