PURPOSE: To realize high speed and high accuracy motion controls of a moving element by supporting bearings on cylindrical and square bar guide rails of a straight line motion mechanism by magnetic resiliency.

CONSTITUTION: A moving element M comprizing a carriage 10 and a No.1 to No.4 bearings reciprocates in parallel to a No.1 and No.2 guide rails 2 and 4. The external surface of a No.1 guide rail 2 is provided with at least four square permanent magnets 3a and 3d the upper and lower surfaces of which are magnetized with N and S poles and the different poles are opposed to each other; the internal surface of a No.1 and No.2 bearings 5 and 7 is provided with the same number of square bar permanent magnets 6a to 6d and 8a to 8d as on the No.1 guide rail, respectively, and the different poles are opposed to each other. The upper and lower surfaces of the No.2 guide rail 4 is constructed of a permanent magnet magnetized with one pole each and the surfaces opposite to a No.3 and No.4 bearings 9a and 9b are constructed of a permanent magnet magnetized with the same kind of pole as these bearings. The respective clearances g1 to g3 are sealed with magnetic fluid h. Thus, the guide rails are supported in the bearings by a magnetic resiliency F under low frictional condition without direct contact with each other.