To improve braking performance of an eddy current type reduction gear quipped with an electromagnet.

The eddy current type reduction gear comprises a brake disc 7 which is fitted to a rotating shaft 1 for generating an eddy current, and an electromagnet 8 fitted to the fixed side to face the brake disc 7. The electromagnet 8 comprises a cylindrical magnetic pole member 9 which is fitted to the fixed side and is coaxially formed with the rotating shaft 1 so that both end surfaces 13 and 14 face the brake disc 7, with the cross section in radial direction being U-shaped, an electromagnetic coil 10 where the electric wire is wound on the rotating shaft 1 of the magnetic pole member 9, and an inductive pole member 11 which extends in the radial direction of the rotating shaft 1 to face the brake disc 7 of the magnetic pole member 9.