Milk was concentrated by commercial tubular membranes, The permeation rate reduction of hydrophilic membranes (sulfonated poly sulfone (SPSf), polyacrylonitrile (PAN), cellulose acetate (CA)) was found not to be large but hydrophobic membranes to be pronounced considerably, In the case of UF concentration total solids, proteins, fats and minerals were increased as concentrated but carbohydrates decreased. NF showed the same behavior except carbohydrates showing small reduction rate.