PURPOSE: To provide a desired outer diameter even if outer diameter of a supplied cable core fluctuates by setting a pair of cross guide roller apparatuses along the proceeding direction of the cable core and installing a plurality of pairs of correcting rolls in the down stream side.

CONSTITUTION: A plurality of pairs of correcting rolls are installed along the cable core C proceeding direction wherein the pairs of correcting rolls are composed by setting correcting rolls face to face while sandwiching the cable core C. Pairs of rolls 2A, 2B are set and aligned in parallel in one direction in the upper stream side of the core C proceeding direction and pairs of rolls 2C, 2D are set and alignes in the direction at right angles to that of the former pairs in the down stream side. A pair of cross guide roller apparatuses 10A, 10B are set in the further upper stream side than the pairs of the rolls 2A, 2B along the core C proceeding direction and roller apparatuses are installed respectively in supporting stands 12A, 12B while one roller apparatus is rotated at 45° to the other roller apparatus. As a result, at the time when the core C is supplied, the core is sandwiched by the apparatuses 10A, 10B from 8 directions and the flatness of the core C is corrected and the outer diameter fluctuation is suppressed to the minimum level.