Charged particle beam system

There is provided a charged particle beam system having a computer system for controlling an acceleration voltage of a charged particle beam emitted from a charged particle source, the system including: a first diaphragm group having first and second diaphragms which are diaphragms that act on the charged particle beam and have different thicknesses; and a first diaphragm switching mechanism for switching the diaphragm in the first diaphragm group, in which the computer system controls the first diaphragm switching mechanism so as to switch from the first diaphragm to the second diaphragm according to an increase or decrease of the acceleration voltage.