Abstract: An ultrapure water production system to produce an ultrapure water, includes a pre-treatment unit 2; a primary pure water production unit 3; a secondary pure water production unit 4; a storage unit 5 provided to precede the pre-treatment unit 2 or between the pre-treatment unit 2 and the primary pure water production unit 3, the storage unit 5 being capable of storing raw water or treatable water; a recovery treatment unit 6 to remove impurities mixed in a used ultrapure water obtained after use of the ultrapure water and containing hydrogen peroxide with passing a part or the whole of the hydrogen peroxide therethrough, to make a recovered water; and a circulator 7 to circulate the recovered water obtained from the recovery treatment unit 6 to feed the recovered water back to the storage unit 5.