Provided is a dehydrator that requires no excessively large apparatus structure and achieves cost-saving while maintaining suction efficiency at a desired level by use of suction means. A dehydrator 100 for separating water from a target liquid 13 includes at least two water separation membrane units 1a and 1b which are provided in series in a flow direction of the target liquid 13. The water separation membrane unit 1a on an upstream side out of the water separation membrane units 1a and 1b is connected to suction means 7 for sucking a gas phase containing water through one condenser 4, and the one condenser 4 condenses water in the gas phase and thereby separates the water. The gas phase sucked by the suction means 7 from the one condenser 4 is transferred to at least one downstream condenser 8 provided downstream of the one condenser 4, and the downstream condenser 8 condenses water in the gas phase and thereby separates the water. The water separation membrane unit 1b on a downstream side of the water separation membrane unit 1a is connected to a steam ejector 3, and the condenser 4 for condensing water in a gas phase passed through the steam ejector 3 condenses water and thereby separates the water.