Novel mutant enzymes of endoglucanase II (EGII) from fungus Trichoderma viride were prepared and their hydrolysis and enzymatic polymerization activities were studied. EGII(core)2 and EGII(core)2-His, which possess sequential two active sites of EGII with a His-tag probe at the N-terminal and with His-tag probes at the N and C terminals, respectively, showed higher hydrolysis activities than EGIIcore with a single active site even in comparison on the active-site concentration basis. These mutant enzymes were applied to the enzymatic polymerization to afford artificial cellulose. The polymerization rates with using EGII(core)2 and EGII(core)2-His were also higher than that with using EGIIcore. The polymerization products were identified as highly crystalline cellulose of type II. The mutant enzymes were also effective to prepare spherulites. EGII(core)2 and EGII(core)2-His are considered to possess higher hydrolysis and polymerization activities than EGIIcore mainly due to the suitably stabilized conformation with the sequential arrangement.