To provide a charged-particle beam device in which a locking mode is not generated near the center of gravity of the device so that a sufficient space can be secured around a sample chamber.

A mirror 1 and a sample chamber 2 are placed on a baseplate 3 which is in the form of a square flat plate. Columns 4a to 4d are mounted on the four corners of the baseplate 3, and support plates 5a to 5d are mounted on the tops of the columns 4a to 4d. Elastic bodies 7a to 7d for absorbing vibrations from a substrate 6, such as spring coils, are placed between each support plate 5a to 5d and the substrate 6. Further, support members 8a to 8d each made from a material with high rigidity are mounted between the sample chamber 2 and each column 4a to 4d.