A sterilizing system according to the present invention includes a water supply apparatus provided with a filter unit having a plurality of filters, a water tank storing water purified by the filter unit, a water cock and water tank connection passages, and a sterilizer to sterilize the water supply apparatus, wherein the sterilizer comprises a sterilizing water generator, a circulation pump, a circulation passage, a rinsing water supply passage, a first drain passage and a first drain valve.