PURPOSE: To form a flexible handle and not to cause a streak and gray fold in a modifying process by specifically treating a fiber cloth comprising tencel in a tension applied state.

CONSTITUTION: Fiber cloth comprising tencel is immersed in hot water at 80-95°C, immediately quenched by sprinkling of cold water kept at 5-20°C and molecular arrangement is fixed to hardly cause streak and gray ford. Then, the fiber cloth is set preferably in a zigzag folded state in the interior of a rotary drum washer and a rodlike separator is inserted into a space between the folded cloth. An aqueous solution containing cellulase as, a cellulose hydrolyzing enzyme is added to the cloth. The cloth is treated with the enzyme while rotating the cloth, and fluff produced in the cloth and fluff occurring during the modification are dropped and removed to give tencel yarn having excellent flexibility, moisture absorption and water retaining properties free from fluff without reduction in strength.