Charged particle beam apparatus

There is provided a charged particle beam apparatus that can reduce the processing time. A charged particle beam apparatus includes: an excitation control unit that controls a focal position by changing a control value of excitation of an electronic lens; an electrostatic field control unit that controls the focal position by changing a control value of an electrostatic field; a focal position height estimation unit that estimates a height of the focal position from the control value of the excitation of the electronic lens; and a control unit that controls the excitation control unit and the electrostatic field control unit. The control unit compares the height of the focal position estimated by the focal position height estimation unit with a height of a sample surface of a sample to be observed, and according to a result of comparison, determines whether it is necessary to change the control value of the excitation of the electronic lens before observing the sample.