Abstract: A method for back-washing a submerged-type ceramic membrane separation apparatus is provided in which filtrate once removed from the apparatus and a chemical agent are forcibly supplied to filtrate passages in ceramic membrane filters to wash the ceramic membrane filters with the filtrate and with the chemical agent, wherein the water washing and chemical washing are carried out at a predetermined frequency ratio and for a predetermined time period, or wherein the frequency and time period of the chemical washing are determined on the basis of a transmembrane pressure difference, suction pressure or filtrate flux observed during a filtering operation performed by the membrane separation apparatus. This method makes it possible to avoid an excessive chemical washing, and to reduce the amounts of water and chemical agent and the time required for the chemical washing.