PURPOSE: To obtain a small-sized filter comprising laminated flat boards with good mass-productivity by connecting electrically the 1st and 2nd resonance circuits and adopting the constitution that both the circuits are coupled magnetically with a coupling coefficient being a specific value or below.

CONSTITUTION: The circuit shown in a figure (a) is split into the 1st and 2nd resonance circuits to the right and left side by a line 4-4' and each circuit constitution is formed respectively on dielectric boards 11, 13 by coating. In this case the 2nd circuit is connected to the high potential side of the 1st circuit. The 1st circuit and the 2nd circuit are coupled magnetically via the mutual inductance M of coils L1 and L2 in the equivalent circuit (c). L1 and L2 are respectively leakage inductances of the coils L1, L2. The value of the coefficient M is changed by the area of the overlapped part 16. The area of the overlapped part 16 is regulated to nearly ≤1/2 of the smaller area among the areas surrounded by the outside pattern of the pattern of the coils L1, L2. Further, the coupling coefficient is brought into ≤0.2∼0.3 by selecting the thickness of a spacer 12 as ≥nearly 0.3∼0.5mm. Thus, the laminated filter is obtained without decreasing the characteristics.