Disclosed herein is a water purifier, in which a partitioning container is detachably mounted on the bottom surface of a tank cover, and an agitator is inserted into the partitioning container to be connected to an agitating motor mounted in the tank cover in a state where the partitioning container is mounted on the bottom surface of the tank cover. By this structure, the inner diameter of the partitioning container may be less than the outer diameter of the blade of the agitator.