PROBLEM TO BE SOLVED: To provide a membrane filtration system and a membrane filtration method which suppress fouling, achieves a stable operation, and remove a suspended material in halide ion-containing water containing halide ions and ammonia nitrogen.SOLUTION: A membrane filtration system 1 removes a suspended material in halide ion-containing water containing halide ions and ammonia nitrogen. The membrane filtration system 1 includes: an ozone treatment apparatus 12 as a peroxide generation means for generating a peroxide in the halide ion-containing water； and a membrane filtration apparatus 16 to filtrate peroxide-containing water with the peroxide generated therein, by using an ultrafiltration membrane or microfiltration membrane.
