Abstract: A water-sealed type vacuum pump characterized in that a suction pipe connected to a chamber to be vacuumized above liquid containing cylinders, which are provided at the lower portion thereof with a mechanism for alternatively increasing and decreasing a pressure of liquid, is open to a lower portion of a suction chamber through an intake valve, the liquid containing cylinders each being interiorly provided with a valve means so as to discharge the liquid through the valve means when the liquid pressure is high while to suck air from the suction pipe when the liquid pressure is low, and a liquid circulating device is provided to return the liquid to be discharged thereby effecting stabilized suction and discharge, the liquid containing cylinders being further interiorly provided with a fluid cooling device to cool and liquidize the sucked air.