An apparatus for winding a heating wire (1) on a core for forming the inner periphery of an electric melt-bonding joint, which comprises a core (6) in a generally cylindrical shape which is capable of roating around its axial center, the core being relatively moved in the axial direction with respect to the heating wire, an engaging piece (7a) mounted on the core, which has a holding portion for holding the heating wire, and a fixing means (5) to fix a terminal pin (1a) to the leading end of the heating wire, wherein the engaging piece has a holding portion (71) for holding the terminal pin, whereby the heating wire is wound on an outer peripheral portion of the core by rotating the core.