To obtain a laminated balun transformer having an excellent electric characteristic, capable of stably attenuating a harmonic wave.

The laminated balun transformer is structured of a lamination 10a having laminated ceramic dielectric layers 11-20. In the lamination 10a, unbalanced signal terminal P1, ground terminal G1, balanced signal terminal P2, balanced signal terminal P3, ground terminal G2 and dummy terminal P4 are formed. In the dielectric layers 13, 15 and 16, there are formed a first line 13a, a second line 15a and a third line 16a, each having a line length sufficiently shorter than a 1/4 wavelength of an input signal wave. The second line 15a is electromagnetically coupled with the first line 13a so as to sandwich the dielectric layers 13, 14, and also electromagnetically coupled with the third line 16a so as to sandwich the dielectric layer 15.