A manual/pneumatic oil pumping device having a housing defining therein an oil reserving space and an upper cover. A floating board is disposed in the oil reserving space. The upper cover is equipped with a manual air sucking mechanism, a pneumatic air sucking mechanism and an oil sucking tube. The pneumatic air sucking mechanism is provided with a controlling unit. The control controlling unit includes a seat body, a valve body, a sleeve and a movable block. The movable block is fitted in the sleeve and has a downward extending projecting post. When the oil is pumped to fill up in the oil reserving space, the projecting post is upward pushed by the floating board to make movable block move upward. At this time, the leakproof washer on the movable block seals the through hole of the seat body and the push pin pushes the valve body away from the through hole so as to block the air sucking passage of the pneumatic air sucking mechanism.