PURPOSE: To increase dispersibility by charging chopped strands of glass wool in the same polarity.

CONSTITUTION: A glass fiber strand S is introduced to a cutter 14 and cut in a given length to obtain chopped strand C which is subjected to fall down into a chamber 10 and to charge in the same polarity by positive ion or negative ion blown from an ion blower 17. Further, each chopped strand C, that has fallen down while being stirred by air flow made by a stirrer 15, is accumulated on a conveyer belt in averaged dispersiveness owing to repulsion to each other by the same polarity of an electrostatic charge on a surface of the strand.