A method of bonding electrodes and core wires capable of shortening the operation time and improving the bonding strength and an electronic unit formed by bonding the electrodes and the core wires are intended to be provided.After supplying a thermosetting resin 8a incorporated with solider particles 7a so as to cover a plurality of electrodes 3 on a substrate 2, arranging each of core wires 6 while opposing vertically to each of the electrodes 3 above the substrate 2, locating a sheet member 11 above the core wires 6, hot pressing each of the core wires 6 and the thermosetting resin 8a by way of the sheet member 11 by hot press bonding tool 12 from above the sheet member 11 to thermally cure the thermosetting resin 8a and melt the solder particles 7a contained in the thermosetting resin 8a, detaching the hot press bonding tool 12 from the thermally cured product 8 of the thermosetting resin 8a, bonding the core wires 6 and the electrodes 3 by the solidification product 7 of solder formed by solidification of a molten product of the solder particles (molten solder 7b) and, finally, peeling the sheet member 11 from the thermally cured product 8.