A dehumidification system including: an exhaust path for exhausting indoor air to the outdoor space; an inlet path for entering outdoor air to the indoor space from the outdoor space; an indoor air bypass path bypassing a part of indoor air to be exhausted to the exhaust path to the inlet path by connecting the exhaust path and the inlet path; an outdoor air bypass path bypassing a part of outdoor air to be flowed to the inlet path to the exhaust path by connecting the inlet path and the exhaust path; and a porous separation membrane filter installed between the indoor air bypass path and the outdoor air bypass path and passing water molecules included in indoor air passing through the indoor air bypass path through the outdoor air bypass path.