Provided are a water treatment system and a water treatment process, which are capable of reproducing water containing salts with high water recovery. A water treatment system 100 comprises a second demineralizing section 210a, 210b that separates water to be treated containing Ca ions, SO4 ions and carbonate ions into concentrated water in which the Ca ions and the SO4 ions are concentrated and treated water; a crystallizing section which is positioned on a downstream side of the second demineralizing section 210a, 210b and which includes a second crystallizing tank 221a, 221b that crystallizes gypsum from the concentrated water and a seed crystal supplying section that supplies seed crystals of gypsum to the second crystallizing tank 221a, 221b; and a separating section that is positioned on a downstream side of the crystallizing section and separates the gypsum from the concentrated water.