To provide a pouring spout that allows a nozzle of a packaging container to be accurately inserted into a pouring spout of a refill container. The above-described problem is solved by a pouring spout (10) provided to a refill container (1) for pouring contents into a packaging container, and for pouring out the contents stored in the refill container (1). The pouring spout (10) comprises at least a bonded part (11) bonded to a pouch main body part of the refill container, a tubular part (12) for pouring out the contents, a flange part (13) jutting outward at a boundary between the bonded part (11) and the tubular part (12), a channel (14) for passing the contents from an inside to an outside of the refill container, and a closing member (20) for opening and closing the channel (14). Both end portions of the flange part (13) separated farthest in a horizontal direction jut slightly outward from an area facing a peripheral wall part of the pouring unit constituting the packaging container.