The invention discloses a retarding device, comprising a gearbox, a gear set and a driving disc, wherein the gear set is arranged in the gearbox and is used for accelerating; the driving disc is used for driving the gear set to rotate; one end of the gearbox is provided with a friction drum; the friction drum is internally provided with a clutch disc and a poking disc; the poking disc is used for poking the clutch disc to rotate; the gear set comprises a gear shaft which extends into the friction drum and drives the poking disc to rotate; the outer edge of the clutch disc is made of an elastic material; the clutch disc is stretched under the action of a centrifugal force during a rotation process, and friction is produced between the outer edge of the clutch disc and the inner wall of the friction drum. The retarding device has the advantages that the clutch disc is made of the elastic material, and the clutch disc is radially stretched under the action of the centrifugal force during the own elastic rotation process, so that the friction is produced between the clutch disc and the inner wall of the friction drum; the larger the rotating speed of the driving disc is, the larger the centrifugal force at the edge of the clutch disc is, thus the frictional force between the clutch disc and the inner wall of the friction drum is larger, and the retarding effect can be effectively and automatically adjusted according to the rotating condition of the driving disc; the retarding device is applied to the field of curtain accessories.