A novel endoglucanase PPCE derived from Penicillium pinophilum, a cellulase preparation containing the endoglucanase PPCE, and a method of treating a cellulose-containing fabric utilizing the endoglucanase PPCE or the cellulase preparation, are disclosed. The endoglucanase PPCE is highly active to a fabric, and has a low optimum temperature and a strongly acidic optimum pH.