PURPOSE: To provide a magnetically activated torque limit joint which can quickly and easily adjust the maximum transmittable torque and transmit torque larger compared to given physical dimensions.

CONSTITUTION: A cylindrical body 16 connected to an input drive shaft 11 is formed of a magnetizable material resistant against magnetizing condition in magnetization. A first hollow cylindrical output drive member 21 is concentrically supported around the cylindrical body 16 so as to be rotatable around the cylindrical body 16. A second output drive member 24 is connected to the first output drive member 21 so as to be extended concentrically in the cylindrical body 16. Plural pairs of magnets 40, 41 are fixed to the first and second output drive members 21, 24 to make a magnetic field generated around the cylindrical body 16. When the input drive shaft 11 and the cylindrical body 16 are rotated, torque to rotate the first and second output drive members 21, 24 together is generated. The first and second output drive members 21, 24 are rotated to enable the relative positions to be changed and accordingly the intensity of the magnetic field generated thereby can be also changed.