An integrated stacked transformer includes a primary inductor and a secondary inductor, and the primary inductor includes at least a first turn and a second turn, and is at least formed by a plurality of windings of a first metal layer and a second metal layer, wherein the first metal layer and the second metal layer are two adjacent metal layers, and the second turn of the primary inductor is disposed inside the first turn; the secondary inductor includes at least a first turn, and the secondary inductor is at least formed by at least one winding formed by the second metal layer, wherein the first turn of the secondary inductor substantially overlaps the first turn of the primary inductor; wherein the second turn of the primary inductor includes a segment of a parallel connection structure constructed by the first metal layer and the second metal layer.