A wet-type dust collector for a vacuum cleaner. The disclosed wet-type dust collector includes a first separating portion, the inside of which is filled with water for separating dust from air that is suctioned in from the outside; an exhaust pipe unit having an exhaust outlet and installed inside the first separating portion; and a passage-closing unit installed inside the exhaust pipe unit, wherein the passage-closing unit closes the exhaust outlet of the exhaust pipe unit by means of the combined forces of the suctioning force through the exhaust pipe unit and the buoyant force of the water, in order to prevent the water from leaking out from the first separating portion.