To reduce the cost and lengthen the service life of a flexible engagement type reduction gear for reducing speed between external teeth of a flexible member for flexibly deforming in a substantially oval shape and internal teeth engaged with a part of the external teeth.

In the flexible engagement type reduction gear, an angular ball bearing 30 interposed between an output member 27 and a fixed case 25 supports the output member 27 and the fixed case 25 while permitting relative rotation between the output member 27 and the fixed case 25. Therefore, load supporting is performed by rolling contact, and as a result, friction hardly occurs, and the service life can be improved. Further, the angular ball bearing 30 is inexpensive compared to a cross roller bearing or a taper roller bearing, so that the reduction gear can be inexpensive.