We have observed the protein cake layer deposited on the membrane surface in dead-end ultrafiltration of bovine serum albumin (BSA) solutions. It is clarified that the protein cake layer mainly forms on the lower part of the membrane surface during inclined ultrafiltration, where the membrane is inclined. After downward ultrafiltration is conducted in the wake of inclined ultrafiltration, the deposited cake layer is spread over the membrane surface. As a result, total filtration resistance R-t dramatically increases. The R-t-value in this case is in accordance with that in downward ultrafiltration, compared with the same filtrate volume.