PURPOSE: To certainly prevent on-sided contact of a burnishing roller by making a head frame equipped with a tool holder to be freely moved in the direction of shaft of a work and permitting a light-weight head frame to be transferred in the axial direction and permitting the shift of position of the work to be absorbed.

CONSTITUTION: A pair of burnishing rollers 6 which are supported onto a tool holder 5 by the advance of a head frame 2 are inserted into between the both shoulder surfaces Wb of a work W which are opposed in the axial direction, and rollers 6 and 6 are widened and operated. In this case, the set position sometimes shifts in the axial direction because of the error, etc. of the working depth of a center hole on the work W, and one roller 6 contacts on-sidedly onto one shoulder surface by the widening operation of the rollers 6 and 6. However, since the head frame 2 is moved freely in the direction of axis of the work W, the head frame 2 is transferred in the axial direction, following the work W, by the repulsive force of the one-sided contact, and correct positoning is permitted, and burnishing rollers 6 and 6 are pressed onto the both shoulder surfaces Wb by a uniform pressure, and thus burnishing work is carried-out. Thus, positioning is carried-out smoothly, and wrong positioning is not generated.