A residual oxidant-eliminating apparatus, a residual oxidant-eliminating method using the same, and a system for sterilizing water thereby are provided to gain removal effect of residual oxidant with inexpensive cost. A water sterilization system(1) includes a sterilizer(10), an aerator(20), a residual oxidant removing unit(30). The sterilizer includes a sterilization tank(11) and the aerator includes an aeration tank(21). The residual oxidant removing unit includes a processing bath(31), an inlet(32), a first fluidized bed(35), a second fluidized bed(36), and an outlet(33). The inlet injects aerated water(38) into the processing bath. The first fluidized bed is installed at the inside the processing bath and formed by activated charcoal(35A).
