PURPOSE: To reduce noise and not to damage a ball by constituting a main ball, small ball, mounting base composing a free ball bearing with a synthetic resin.

CONSTITUTION: A free ball bearing 10 is constituted so that a flange part 13a is arranged at both sides or the outer periphery upper part of a mounting base 13 and the main body of a lower mounting base 13 is inserted into the mounting part arranged on the table upper face, is fixed. A half spherical recessed part 13c is formed on the center of the mounting base 13, a small balls 14.14... are arrayed to an extent to approximately cover the surface of recessed part 13c, a large diameter main ball 15 is placed on the small balls 14.14... so as to be arranged free to rotate in the recessed part 13c. An edge part 13d is formed at the upper part of mounting base 13 so that the main ball does not easily go out. Further, the mounting base 13, small ball 14, main ball 15 are respectively composed of a synthetic resin, for example polyurethane.