To provide a laminated balun transformer in which the adjustment of the electromagnetic coupling of a transmission path can be performed easily, and which can be made compact in size.

This laminated balun transformer, where the stack having a dielectric layer and a conductor layer is equipped with a first transmission path, a second transmission path to be electromagnetically coupled with that first transmission path, and a third transmission path, and for the first transmission path, one end is connected to an unbalanced terminal and the other end becomes an open end, and for the second transmission path, one end is grounded and the other end is connected with a first balanced terminal, and for the third transmission path, one end is grounded and the other end is connected with a second balanced terminal, and here the first, second, and third transmission paths are constituted severally by electrically connecting a plurality of conductor layers divided into the plural dielectric layers, and this possesses a first laminating region which is constituted by laminating a plurality of dielectric layers, where a pair of conductor layers constituting the first and second transmission paths and a second laminating region which is constituted by laminating a plurality of dielectric layers where a pair of conductor layers constituting the above first and second transmission paths are made, and is equipped with a grounding electrode which is made of a conductor layer having a spread, between the first laminating region and the second stacking region.