An electrical connector comprising, a plug connector and a receptacle connector for receiving the plug connector fitted therewith, said receptacle connector including a cylindrical receptacle shell provided on its outer circumference with fitting means extending circumferentially about a fitting axis, said plug connector including a cylindrical plug shell having a portion to be inserted into an inner aperture of said receptacle shell and a flange provided on an outer circumference of the plug shell, a cylindrical coupling ring surrounding the outer circumference of the plug shell and rotatable and holding said flange of the plug shell on its forward and rearward sides, said coupling ring having on its inner circumference fitting means adapted to be fitted with said fitting means provided on the receptacle shell and a retainer ring located on the side of the flange opposite to said portion of the plug shell to be inserted into the receptacle shell, key means provided between the inner bore of said receptacle shell and the portion of the plug shell to be inserted into the inner aperture of said receptacle shell for preventing relative rotation between the plug and receptacle shells, at least one wave-shaped annular spring interposed between the flange and the retainer ring, said wave-shaped annular spring being rotatable together with the coupling ring, said wave-shaped annular spring and the flange being formed in their opposed surfaces with at least one protrusion and at least one recess, respectively, to form click lock means, the protrusion and the recess being oriented to be coincident in position with each other and detachably fitted with each other when said plug connector and said receptacle connector have been fitted, said plug connector and said receptacle connector being brought into coupling condition by rotation of said coupling, said electrical connector including a base insulator having at least one contact insert aperture and a contact inserted and anchored at the contact insert aperture, said contact being removable from the contact insert aperture of the base insulator by tool insertion from a connector fitting side, a cover insulator detachably secured to the base insulator on the connector fitting side and having a through-hole communication with said contact insert aperture of the base insulator and having a diameter smaller than that of the contact insert aperture, thereby enabling said through-hole to guide insertion of the contact, said cover insulator being provided with mounting protrusions for mounting the cover insulator on the base insulator, each of the mounting protrusions including a small diameter pin formed at its end with beveling and a larger diameter pin formed at the bottom of the mounting protrusion, thereby detachably securing the cover insulator to the forward surface of the base insulator by press-fitting the mounting protrusions into openings in the base insulator.