Abstract: A water drinking device for pets comprises a vessel provided at the top thereof with a cap having a ventilation hole. The vessel is further provided at the lower end thereof with a slanted bottom so as to ensure that the water outlet is located at a level higher than the bottom end of the vessel and that the water flowing out of the water outlet is free from impurities. The vessel is further provided peripherally at different levels thereof with a plurality of locating slots, each of which is provided respectively at both ends thereof with a locating recess engageable with a locating projection of the retaining arm of a vessel hanger.