A water treatment apparatus includes a raw water supply tube, mixed raw water stream jet nozzles each communicating at one end thereof with the raw water supply tube and having at the other end thereof a raw water outlet from which mixed stream of raw water and air is jetted out, a filtering tank housing a filter layer disposed below the mixed raw water stream jet nozzles with a predetermined distance between the surface of the filter layer and the raw water outlet of the mixed raw water stream jet nozzles, a filtered water takeout tube provided in the filtering tank for taking out water filtered through the filter layer, a reverse stream cleaning water supply tube provided in the filtering tank for supplying reverse stream cleaning water to the filter layer, filter layer cleaning jet nozzles each communicating at one end thereof with a filter layer cleaning water supply tube and having at the other end thereof a cleaning water outlet from which cleaning water is jetted out, and an overflow outlet provided in the filtering tank above the filter layer.