Method for regenerating membrane cartridge

To provide a method for regenerating a membrane cartridge for MBRs, whereby it becomes possible to recover or further improve the lost separation performance of the membrane cartridge for MBRs while keeping the cartridge structure thereof, and it becomes also possible to maintain high water permeability and fouling resistance of the membrane cartridge for a long period. A method for regenerating a membrane cartridge that has been used in the solid-liquid separation of active sludge, said method being characterized in that a washing step using first chemical substance-containing water, a washing step using water, a first hydrophilization step using a hydrophilization solution, a drying step and a second hydrophilization step using a hydrophilization solution are carried out in this order.