PURPOSE: To provide the subject method comprising such a practice that an opening device for withdrawing fiber tufts from fiber bales is lowered and then passed in the same rotational direction and subsequently passed, without being lowered, in the reverse and/or the same rotational direction to increase the amount of a fiber material to be withdrawn.

CONSTITUTION: This method comprises the following practice: a fiber bale 1 with a height dimension C is compressed to a dimension b with a grate rod 7, an opening device 5 is then lowered by a dimension (a) and allowed to travel in the same rotational direction (see arrows A and C) to work the dimension (a) by an opening drum 8; thereafter, the opening device 5 is allowed to travel in the reverse rotational direction without being lowered to work only the fiber material raised owing to the elasticity of the bale 1; thus the fiber material is withdrawn by the opening device through both its traveling directions.