Low-cost protein purification methods are in high demand for mass production of low-selling price enzymes that play an important role in the upcoming bioeconomy. A simple protein purification method was developed based on affinity adsorption of a cellulose-binding module-tagged protein on regenerated amorphous cellulose (RAC) followed by modest desorption. The biodegradable cellulosic adsorbent RAC had a very high protein-binding capacity of up to 365mg of protein per gram of RAC. The specifically-bound CBM-protein on the external surface of RAC was eluted efficiently by ethyl glycol or glycerol. This protein separation method can be scaled up easily because it is based on simple solid/liquid unit operations. Five recombinant proteins (CBM-protein), regardless of intercellular or periplasmic form, were purified successfully for demonstration purpose.