The invention provides a process for manufacturing at low cost cellulose acetate, which is useful as a biodegradable plastic, using corncob meal which has hitherto been thrown away as a raw material. More specifically, the invention provides a process for manufacturing cellulose acetate, which comprises the steps of: steaming corncob meal at a temperature of 150 to 250 C. and a pressure of 20 to 29 MPa; filtering the steamed corncob meal to obtain a solid product; and dehydrating and acetylating by adding acetic anhydride and sulfuric acid to the solid product. The steaming is preferably carried out by using a pressure vessel and the filtering is preferably carried out by using a filtering device.