The pumping device includes a barrel, a cover, a pumping mechanism, a positioning ring, and plural posts. The barrel has plural first positioning portions extending upward near a bottom thereof. The cover is disposed on the barrel to selectively close the barrel. The pumping mechanism is disposed on the cover for pumping liquid in the receiving space outward or pumping liquid outside into the receiving space. The positioning ring is detachably combined by two semi-ring bodies and is sleeved onto the cover and the barrel to position the cover on the barrel. The positioning ring has plural second positioning portions. Each of the posts connects the positioning ring and the bottom of the barrel therebetween. Each post is detachably connected to one of the first positioning portions and one of the second positioning portions therebetween so that the two semi-ring bodies are unable to separate freely.