Water treatment apparatus includes raw water special air mixing nozzles (7); filtering tank (5) housing filter layer (4) including two layers of upper layer (2) and lower layer (3), the upper layer including a filter medium with a smaller specific gravity and a larger particle size than a filter medium of the lower layer; a water collection pipe (13) removing filtered water and supplying reverse cleaning water to the filter layer during reverse cleaning; drainage trough (12); and upper layer cleaning apparatus (10), in which the upper layer cleaning apparatus includes upper layer cleaning pipe support member (17), upper layer cleaning water pipe (18), surface-cleaning special air mixing nozzles (19), air suction pipe (20), and horizontal air pipes (31 and 32) and the raw water special air mixing nozzles (7) are attached to raw water inflow tank (70) provided on a part of the drainage trough (12).