A laminated balun transformer subminiaturized with a transmission line length reduced below λ/4 without any variation of characteristics. The laminated balun transformer includes a first strip line having one end inputted to a unbalanced signal; a second strip line having connected to the first strip line; a third strip line formed in parallel with the first strip line and connected to a ground and connected to the external electrode for a first balanced signal; a fourth strip line formed in parallel with the second strip line and connected to the external electrode for a ground and the external electrode for a second balanced signal; and a capacitance forming electrode formed in parallel with a portion of the opened end of the second strip line and connected to the external electrode for the unbalanced signal.