Provided are a stiffener for connecting a prestressed concrete beam and a method of constructing a structure using the same, in which the beam such as the prestressed concrete beam which is covered with concrete is connected to a target structure including a column structure or a girder. The stiffener is made up of a buried stiffener, an end face stiffener, and a joint stiffener, thereby enabling simple connection, excellent stress transmission, and very efficient construction of (building) structures.