PURPOSE: To always keep the attitude of a moving body constant by making it possible to adjust the magnetic force of a magnetic means for applying preload to the bearing face of a static pressure guide device with a gap adjusting screw.

CONSTITUTION: A magnetic means for applying preload to the static pressure bearing 2 of a moving body 1 is composed of a permanent magnet 3 and yokes 4 provided at both sides, and the yokes 4 are made to face to a magnetic substance guide 8. The yokes 4 and the permanent magnet 3 are attached to a non-magnetic substance 5. Adjusting screws 6 are secured to the mounting plate 5 to adjust the gap between the yokes 4 and a quide 8. Optimum preload for maintaining the attitude of the moving body 1 constant can, therefore, be applied by operating the adjusting screws 6.