PURPOSE: To provide a fiber-opening cylinder eliminating a catch of the fiber by setting a groove width of an upper edge part of a groove slightly smaller than the width of a foot portion of a saw-tooth wire fillet before the insertion the saw-tooth wire fillet so as not to form a gap between the tooth wire and a cylinder body.

CONSTITUTION: This fiber-opening cylinder of an open-end spinning machine is formed so that the material of an upward end part 11 smaller than the width (b) of a foot portion 10 is deformed in the side direction at the position of a saw-tooth wire fillet 12 by the foot portion 10 so as to form the upper edge part 11 of the groove 9 precisely fitting with the side surface of the foot portion 10 upon inserting the foot portion 10 of the saw-tooth wire fillet 7 into a helical groove 9 formed at the outer peripheral surface 8 of a cylinder body 6.