Abstract: An adjustable one-way rotary liquid pumping device including a housing, a cover fixedly engaged with the housing, a first bearing a first bearing fitted in the housing, a second bearing fitted in the cover, an axle extending through the housing and the cover and supported by the two bearings, a rotor fixedly mounted on the axle and having a plurality of pawls, a collar enclosing the rotor, a seat having two protuberances supporting the collar thereby locating the collar at an eccentric position with respect to the axle, a plurality of rollers each fitted between every two of the pawls of the rotor, a plurality of springs urging respective rollers against an inner wall of the housing and an inclined side of the pawls, and an adjustable valve fitted through the housing, the collar, and the seat, whereby the liquid can be pumped in one direction only and the speed of the axle can be adjusted as required.