Abstract: The invention relates to a tail gas treatment device and a tail gas treatment method. The tail gas treatment device comprises: a gas inlet; a gas circulation passage connected with the gas inlet; a first water orifice used for spraying water to the tail gas in the gas circulation passage; a waste water pool used for accommodating waste water generated from treating the tail gas; a gas outlet; a water quality detection unit used for detecting water quality of waste water in the waste water pool; a drainage port used for draining waste water in the waste water pool; and a water return port connected with the first water orifice via a water return pipeline, and used for delivering water in the waste water pool to the first water orifice when the water quality of the water in the waste water pool meets a recycling requirement.