To provide a guide pin for electric resistance welding electrodes, which has superb retention of a magnet, high strength and rigidity, and is easy to fabricate.

In one of pin member 21 with a circular cross section, a retaining hole 22 to retain a magnet 30 is formed in a coaxial state with the axis line O-O of the pin member 21. In the other pin member 24 with a circular cross section, a cavity section, which is inserted into the retaining hole 22 and encloses the magnet 30, is formed in the coaxial state with the axis line O-O of the retaining hole 22. In a state in which the cavity section is inserted into the retaining hole 22 and the magnet 30 is enclosed, the peripheral joining portions of both pin members 21, 24 are welded. Thus, a highly accurate guide pin 15 is obtained and the magnet 30 is retained inside the guide pin 15 in a secured condition.