PURPOSE: To embody a torque limitter which reduces torque with convensional viscous fluid being utilized as resistance.

CONSTITUTION: An endless sealed flow passage 2 in which oil is sealed is formed on a main body 1, while a circular empty chamber 5 is formed on a proper portion of the sealed flow passage 2. A trochoid pump A is rotatably assembled with a clearance of a reference value in respect to an inner peripheral surface of the empty chamber 5. Outflow and inflow ports 8, 8' are opened to the sealed flow passage 2. A shaft 14 of an internal gear 7 of the trochoid pump A serves as an input/output shaft 13, which shaft 14 is projected outside of the main body 1.