A medical stent is provided including a longitudinal member which has an internal space and a side opening that communicates with the internal space； a flap portion which has an extension portion that extends radially outward from a side surface of the longitudinal member and a fixed portion that is fixed to the longitudinal member, being continuous with the extension portion, and is transformable between an open state in which the extension portion radially extends from the side surface and a closed state in which the extension portion extends along a longitudinal axis of the longitudinal member； and a flap radial-expansion prevention portion which prevents a transformation of the flap portion from the closed state to the open state by the flap portion being engaged with an insertion member that extends from the flap portion to the internal space through the side opening and is arranged in the internal space.
