A water purifier capable of stably discharging residual water from an extraction unit is disclosed. The water purifier (100) comprises: a filter unit (110) having a reverse osmosis membrane filter (113) for filtering incoming water; an extraction unit (160) for providing purified water filtered by the filter unit (110) to a user; and a residual water drainage unit (150) configured to drain, through the reverse osmosis membrane filter (113), residual water remaining in the extraction unit (160), by using an osmotic phenomenon of the reverse osmosis membrane filter (113) after completion of the extraction through the extraction unit (160).