Ultrapure water production system, ultrapure water production supply system, and method for cleaning same

The present invention supplies ultrapure water having excellent water quality to a water use point in a short period of time so that contaminants within an ultrapure water production system are not supplied to the supply pipe leading to the water use point during sterilization and cleaning, and contamination of the system by contaminants captured by means of a fine-particle removal membrane is prevented after sterilization and cleaning. An ultrapure water production system at least provided with a tank (11), a pump (12), a heat exchanger (13), an ultraviolet device (14), an ion-exchange device (15), and a first fine-particle removal membrane device (16), wherein a second fine-particle removal membrane device (17) is disposed parallel to the first fine-particle removal membrane device (16), a portion of sterilization water and flushing water is supplied to the first fine-particle removal membrane device (16) and is discharged from the water-supply side to a concentrated water side without passing through the membrane, and the remainder is passed through the second fine-particle removal membrane device (17).