PURPOSE: To twist a strip of flat material into a helix by making twisting rollers freely rotatable to a guiding, holding means for guiding and locating the strip on its plane and making the twisting rollers freely rotatable around the vertical axis of the strip.

CONSTITUTION: A strip 10 is guided to a guide port 18 by pinch rolls. The strip 10 passes through guide rolls 23 and 24, and is held by wheels 28 and 29. At the time of start, the wheels 28 and 29 parallel the guide rolls 23 and 24, and the strip 10 has not yet been twisted. By rotating a handle 44, and by rotating a housing part 21 to a housing part 20, the wheels 28 and 29 are tilted to the guide rolls 23 and 24. By this tilt, the helical pitch of the strip 10 is determined. The strip 10 is subjected to regulation by the chamfered parts 32 and 35 of the wheels 28 and 29 and flange parts 31 and 34, and is formed in a helical shape.