Abstract: A quantitative feeding device includes a housing being funnel-shaped, a hollow ball valve capable of sealingly seating in the housing and vertically rotating with respect to the housing between a first and a second positions. The ball valve has an open top and a radial protrusion defining the first position at which the open top upwardly faces when the protrusion contacts with a side wall of the housing and defining the second position at which the open top downwardly faces when the protrusion contacts with an opposite side wall of the housing. An actuating medium for rotating the ball valve between the first and second positions, an elastic member for usually urging the ball valve at the first position, and an oscillating element capable of contacting with the radial protrusion in the course of rotation between the first and second position in order to be oscillating.