A water treatment device capable of filtering out iron and manganese in raw water by oxidizing them and making them insoluble in water includes a raw water supply tube (4), one or more jet nozzles (5), each being at one end portion thereof in communication with the raw water supply tube (4) and having at the other end thereof a raw water jetting outlet for blowing out the raw water in a jet stream, one or more air introducing tubes (6) provided in correspondence to the jet nozzle or jet nozzles (5), each being at one end portion thereof opened to the atmosphere and being at the other end portion thereof opened to the inside of a corresponding one of the jet nozzles (5) upstream of the raw water jetting outlet and a filter container (3) containing a filter layer (2).