A coaxial connector device comprising: an insulating base provided to be placed on a surface of a circuit board, a signal-joining contacting conductor fixed to the insulating base and provided with a contact connecting portion for projecting from the insulating base and an signal-connecting portion provided to be connected to a signal terminal provided on the circuit board, and a grounding contacting conductor fixed to the insulating base and provided with a cylindrical side wall portion for surrounding the contact connecting portion of the signal-joining contacting conductor along the surface of the circuit board, a plurality of ground-connecting portions provided to be connected to ground-potential terminals provided on the circuit board, and a plurality of connecting portions provided for connecting an annular end of the cylindrical side wall portion with each of the ground-connecting portions, characterized in that the signal-connecting portion of the signal-joining contacting conductor is provided on an end portion of the insulating base facing close the surface of the circuit board so as to extend in parallel with said end portion of the insulating base, in that the ground-connecting portions of the grounding contacting conductor are provided on the end portion of the insulating base so as to extend in parallel with said end portion of the insulating base around the contact connecting portion and the signal-connecting portion of the signal-joining contacting conductor, in that at least one groove (16: 42: 44) is formed on the end portion of the insulating base between the ground-connecting portions of the grounding contacting conductor and the contact connecting portion of the signal-joining contacting conductor and between the ground-connecting portions of the grounding contacting conductor and the signal-connecting portion of the signal-joining contacting conductor so as to surround continuously or intermittently the contact connecting portion and the signal-connecting portion of the signal-joining contacting conductor, and in that at least one of the connecting portions of the grounding contacting conductor is deformed to become distant from the signal-joining contacting conductor. an insulating base provided to be placed on a surface of a circuit board, a signal-joining contacting conductor fixed to the insulating base and provided with a contact connecting portion for projecting from the insulating base and an signal-connecting portion provided to be connected to a signal terminal provided on the circuit board, and a grounding contacting conductor fixed to the insulating base and provided with a cylindrical side wall portion for surrounding the contact connecting portion of the signal-joining contacting conductor along the surface of the circuit board, a plurality of ground-connecting portions provided to be connected to ground-potential terminals provided on the circuit board, and a plurality of connecting portions provided for connecting an annular end of the cylindrical side wall portion with each of the ground-connecting portions, characterized in that the signal-connecting portion of the signal-joining contacting conductor is provided on an end portion of the insulating base facing close the surface of the circuit board so as to extend in parallel with said end portion of the insulating base, in that the ground-connecting portions of the grounding contacting conductor are provided on the end portion of the insulating base so as to extend in parallel with said end portion of the insulating base around the contact connecting portion and the signal-connecting portion of the signal-joining contacting conductor, in that at least one groove (16: 42: 44) is formed on the end portion of the insulating base between the ground-connecting portions of the grounding contacting conductor and the contact connecting portion of the signal-joining contacting conductor and between the ground-connecting portions of the grounding contacting conductor and the signal-connecting portion of the signal-joining contacting conductor so as to surround continuously or intermittently the contact connecting portion and the signal-connecting portion of the signal-joining contacting conductor, and in that at least one of the connecting portions of the grounding contacting conductor is deformed to become distant from the signal-joining contacting conductor.