To provide a series of valve driving devices for setting according to service use on rotational efficiency and reverse rotation preventive functionality of a valve element while reducing the size and a space of the devices.

A series of the valve driving devices 500 drivably constitute the valve element via a speed reducer 300. At least one stage of a speed reduction mechanism of the speed reducer 300 is provided with an input shaft 202, an external teeth gear 206 for eccentrically and rockingly rotating around the input shaft 202, an internal teeth gear 204 for internally meshing with the external teeth gear 206, and a carrier 208 capable of absorbing a rocking component among the rocking component and an autorotation component of the external teeth gear 206. It is composed of an eccentric rocking internally meshing planetary gear mechanism 360 for fixing either one side of the internal teeth gear 204 or the carrier 208, and connecting the other side to the valve element side, and constitute at least two kinds of valve driving devices 500 for laying stress on the reverse rotation preventive functionality and the rotational efficiency by imparting a difference to eccentric rocking rotational resistance of the external teeth gear 206.