The cyclo gear reducer has a deceleration ratio ofengagement that is two and three times higher than the usual spur wheel or involute gears. Since the curved shape of the teeth used in an epitrechoid gear are not sharp, the gear can be made using a 3D processing. Our purpose is to develop the cyclo gear reducer that can semi-eontinuously change the deceleration ratio by instatling the mechanism where the slide moves along the direction of the rotation axis in the epitroehoid geag as one ofthe applications of the eycle gear reducer.