A magnet-equipped projection welding electrode, the electrode comprising: a main body made of metal and having a cylindrical shape; an end cover made of metal, the end cover attached to an end of the main body, the end cover having a through hole into which a part is inserted; a heat insulating guide sleeve made of an insulation material, the heat insulating guide sleeve being inserted into the main body and having a minor diameter hole and a major diameter hole, the minor diameter hole communicating with the through hole of the end cover, the major diameter hole having a diameter larger than a diameter of the minor diameter hole; a cooling water passage formed in an outer peripheral portion of the heat insulating guide sleeve or an inner peripheral portion of the main body, the cooling water passage having an annular shape and disposed in a circumferential direction of the main body; an inlet and an outlet formed in the main body, the inlet configured to supply cooling water to the cooling water passage, the outlet configured to discharge the cooling water from the cooling water passage; a heat insulating portion being a portion of the heat insulating guide sleeve that is located at an inner side of the cooling water passage; a container slidably inserted into the major diameter hole located on an inner side of the heat insulating portion, the container containing a permanent magnet; and a magnetic force transmission member extending from the container, the magnetic force transmission member slidably inserted into the minor diameter hole, wherein the permanent magnet, the heat insulating portion of the heat insulating guide sleeve, and the cooling water passage are disposed in a positional relationship in which the permanent magnet, the heat insulating portion of the heat insulating guide tube, and the cooling water passage are arranged in a diameter direction of the main body, characterized in that: a depth dimension of the cooling water passage as viewed in the diameter direction of the main body is set to be smaller than a thickness dimension of the heat insulating portion, wherein a ratio (T1/D1) of the thickness dimension to the depth dimension is set to 1.40 to 1.70. a main body made of metal and having a cylindrical shape; an end cover made of metal, the end cover attached to an end of the main body, the end cover having a through hole into which a part is inserted; a heat insulating guide sleeve made of an insulation material, the heat insulating guide sleeve being inserted into the main body and having a minor diameter hole and a major diameter hole, the minor diameter hole communicating with the through hole of the end cover, the major diameter hole having a diameter larger than a diameter of the minor diameter hole; a cooling water passage formed in an outer peripheral portion of the heat insulating guide sleeve or an inner peripheral portion of the main body, the cooling water passage having an annular shape and disposed in a circumferential direction of the main body; an inlet and an outlet formed in the main body, the inlet configured to supply cooling water to the cooling water passage, the outlet configured to discharge the cooling water from the cooling water passage; a heat insulating portion being a portion of the heat insulating guide sleeve that is located at an inner side of the cooling water passage; a container slidably inserted into the major diameter hole located on an inner side of the heat insulating portion, the container containing a permanent magnet; and a magnetic force transmission member extending from the container, the magnetic force transmission member slidably inserted into the minor diameter hole, wherein the permanent magnet, the heat insulating portion of the heat insulating guide sleeve, and the cooling water passage are disposed in a positional relationship in which the permanent magnet, the heat insulating portion of the heat insulating guide tube, and the cooling water passage are arranged in a diameter direction of the main body, characterized in that: a depth dimension of the cooling water passage as viewed in the diameter direction of the main body is set to be smaller than a thickness dimension of the heat insulating portion, wherein a ratio (T1/D1) of the thickness dimension to the depth dimension is set to 1.40 to 1.70.