To vary the impedance of a matching circuit by one circuit in two dimensions on a Smith chart by connecting an RF probe to a 1st line of the matching circuit and a short-circuit probe which grounds a signal line to a 2nd line, and adjusting the impedance by adjusting the connection positions of the respective probes.

The signal line and ground line of an RF probe are connected at contact positions 11 and 12. Further, the short-circuit probe has a short-circuit probe signal line connected onto the signal line 9 and a short-circuit probe ground line connected onto the ground 3 at a contact position 13. At this time, the signal line 9 is grounded but is separated from a signal line 2 by a capacitor 8, and the grounding does not extend to the signal line 2. Then when the contact positions 11 and 12 are changed, a short-circuit stub 2b and a coplanar line 2c change. Further, when the contact position 13 is changed, a short-circuit stub 9a can be varied independently in length, and consequently the impedance can be varied in two dimensions on the Smith chart.