Eccentric swing type speed reducer

The invention provides a technology capable of suppressing peeling on a rolling surface of an eccentric body bearing. An eccentric swing type speed reducer is provided with: an internal gear; an outergear which is meshed with the inner gear; an eccentric body for swinging the external gear; an eccentric body bearing disposed between the eccentric body and the external gear, wherein the eccentricbody bearing has a roller (60), the roller (60) has an intermediate portion (70) in the axial direction of the roller and a convex surface portion (72) having an outer diameter gradually decreasing from the intermediate portion (70) toward an end portion in the axial direction of the roller, and the convex peak portion height Rpk of the convex surface portion (72) is 0.063 [mu] m or less. 本发明提供一种能够抑制偏心体轴承的滚动面上的剥离的技术。一种偏心摆动型减速装置，其具备：内齿轮；外齿轮，与内齿轮啮合；偏心体；使外齿轮摆动；及偏心体轴承，配置在偏心体与外齿轮之间，其中，偏心体轴承具有滚子(60)，滚子(60)具有滚子轴向上的中间部(70)及外径随着从中间部(70)朝向滚子轴向上的端部而逐渐变小的凸面部(72)，凸面部(72)的突出峰部高度Rpk为0.063μm以下。