The purpose of this study is to investigate the softening effect of cellulase-treated cotton fabric and the damage on the fabric which is accompanied by the treatemnt. Cotton fabric is treated with cellulase under various concentrations and time, and the weight loss, hand values (by KES), surface characteristics, moisture regain, tensile strength, copper number and intrinsic viscosity of the treated samples and untreated samples have been compared. The results are as follows: 1. The weight loss of cotton fabric increased as the concentration of cellulase and the treating time increased. 2. The enzyme treatment had little effect on the stiffness of the treated samples but anti- drape stiffness decreased for the treated samples. Fullness and softness of the treated samples increased and crispness decreased with the lowest level reaching after two hours of the treatment for all concentrations. Scrooping feeling of the treated samples increased and flexibility with soft feeling increased as the treating time and the concentration of cellulase increased. 3. Moisture regain of the samples decreased as the treating time and the concentration of the enzyme increased and the treated fabric showed cracks on the fiber surface, and much surface fibers on the fabric have been removed after the treatment. 4. Tensile strength of the samples decreased as the treating time and as the concentration of cellulase increased, and the copper number increased while the intrinsic viscosity decreased as the treating time increased, but cellulase concentration had a little effect.