PURPOSE: To provide a base held by springs, rubbers, the air, and the like on a stand, and to obtain a means to suppress a vibration of the base resulting from the reaction generated in the switching time or in the step feeding time of a stage provided on the base and moving straightly, by a means of a compact size and a low cost.

CONSTITUTION: A base 8 is held on a stand 10 through spring cushions 11a to 11d, and an x stage 2, a y stage 4, a detecting optical system 7, an x lock device 13, and a y lock device 14 are provided on the base 8. When the x stage 2 is switched, the x lock device 13 is operated to combine the base 8 and the stand 10. And when the y stage 4 is step-fed, the y lock device 14 is operated to combine the base 8 and the stand 10. When such operations are not carried out, the lock devices are released, the base 8 is put on the spring cushions, and the vibration from the outer side is removed. Since the vibration of the base 8 is absorbed to the stand 10, the vibration of the base 8 is very small. As a result, the relative displacement of the detecting optical system 7 and the base 8 is reduced to 0.1μm from the conventional value 0.5μm, and the detecting accuracy of a pattern and a foreign matter on a wafer is improved drastically.