In the search for a plate-shaped solid support for enzyme immobilization, we found commercially obtainable polyethyleneimine (PEI)-cellulose thin-layer chromatography (TLC) plates to have adequate physical and chemical properties for enzyme immobilization. Through Benedict’s, Tollens’ and ninhydrin tests, the PEI-cellulose coating proved to have enough physical strength and amine concentration, and its properties could be maintained nearly constantly during the processes of enzyme immobilization. To confirm that the PEI-cellulose TLC plate was a suitable support for enzyme immobilization, alkaline phosphatase was immobilized using glutaraldehyde as a crosslinking reagent. The activity of the immobilized alkaline phosphatase was assayed with a reiterative method using p-nitrophenyl phosphate as a substrate. By analyzing Lineweaver-Burk plots from the results of successive assays, we proved the immobilized alkaline phosphatase to be reusable many times.