PURPOSE: To prevent the function deterioration of a precision instrument due to the leakage magnetic flux and obtain adequate vibration-proofing by providing multiple legs on a surface plate, providing linear motors between a frame and lower sections of the legs, and covering the linear motors with magnetic shielding members.

CONSTITUTION: A surface plate 20 mounted with a precision instrument 1 is supported by air springs 50 which are passive braking pieces on a frame 40 fixed on a floor 3 with leveling bolts 31. Linear motors 11-13 vibrate legs 21 of the surface plate 20 in the X-direction, Y-direction and Z-direction respectively to perform passive vibration-proofing of the surface plate 20. The linear motors 11-13 are covered with magnetic shielding members 22. Adequate vibration- proofing can be performed with no function deterioration of the precision instrument due to the leakage magnetic flux.