PURPOSE: To prevent generation of noise by interposing upper pieces of a support frame between sliding ball groups on the upper side and the lower side of a rotatable caster, rotatably assembling the upper pieces to a main spindle as one of ball bearers for sandwiching the sliding ball group, and pressing the ball bearer against the sliding ball group by an elastic plate laminated thereto and assembled to the main spindle.

CONSTITUTION: A spiral part 11 and a flange part 12 are provided on the upper part of a main spindle 7 and at the central part thereof respectively, upper ball bearers 9 and upper pieces 2 of a support frame 1 are interposed between the flange part 12 and lower ball bearers 8 fixed at the bottom end part of the main spindle 7 so as to make them vertically movable and assembled to the main spindle 7, the upper sliding ball group 6 and a lower sliding ball group 6' are sandwiched by upper ball bearers 9 and the upper pieces 2, and the upper pieces 2 and the lower ball bearers 8 respectively, the upper ball bearers 9 and the upper pieces 2 of the support frame 1 are energized downward in the direction of the lower ball bearers 8 so as to press respective boards 2, 8, 9 against the respondent sliding ball groups 6, 6'. In the case of floating from a floor face, no clearance is produced between the ball bearers and the sliding bodies so as to reduce noise generation.