The present invention relates to a connection structure in which an inner conductor is combined with a detachable impedance compensator as well as a coaxial connector, an extendible pin and an impedance compensator used for the connection structure. Further, this invention relates to a microwave device connected both electrically and mechanically with the connection structure. An impedance compensation thereof means compensates electric discontinuities between the inner conductor and the extendible pin by mechanical arraying with a microwave device to be combined with the connection structure, whereby the protrusion formed at the impedance compensation means satisfies the conditions, b≦a/5 and c≦2b, when diameter of the impedance compensation means is a, thickness thereof is b, and size of the protrusion is c.