PURPOSE: To reduce the impedance matching time by thinnly dividing part of a capacitance stub in advance and causing solder to flow to the split parts.

CONSTITUTION: In an impedance coupling circuit such as an inter-stage circuit of a microwave circuit, part of the capacitive stub 3 is thinly split in advance and solder is applied to the split parts 30 by a length required for the stub. In this case, in sticking an insulation sheet to the rear side of the capacitive stub 3, the split stub pieces are incorporated via the insulation sheet to facilitate the soldering processing at impedance matching. Thus, the impedance matching is reduced.