To provide a means for suppressing an increase of cost due to complexity and enlargement of a structure of a transmission and an increase in the number of parts regarding the fact that a clutch capacity does not function sufficiently under a high load.

A torque transmission device includes a low torque input means 8, an output rotating means 11 magnetically coupled to the low torque input means, and a high torque input means 15 engaged with the output rotating means 11 and transmitting torque during high-load rotation. The low torque input means 8 includes pole teeth 9 opposed to magnetic poles 12 of the output rotating means and magnetically coupled during low-load rotation, and side magnetic bodies 10 opposed to the magnetic poles 12 slid by a thrust force generated by the relative rotation of the magnetic poles 12 and the pole teeth 9 and magnetically coupled during the high-load rotation. The output rotating means includes the magnetic poles 12, a magnet 13 sandwiched between the magnetic poles 12, and an engagement clutch section 14 engaged with the high torque input means 15 during the high-load rotation.