A cycloid speed reducer has a housing for accommodating a piece of equipment. Outer pins in meshing engagement with cycloid gears of a reduction gear portion are incorporated into the housing as a sliding bearing. A lubrication ring for lubricating the outer pins is slidably incorporated into the housing. The outer pins are lubricated by the outer pin lubricating ring. Inner pins are lubricated by a lubricating ring. The pair of cycloid gears are lubricated via the outer pins and the inner pins. As a result, friction between components is reduced, whereby frictional resistance decreases and durability is enhanced. In addition, the cycloid speed reducer can be manufactured as a small, compact unit.