A high-quality image is acquired while maintaining an improvement in throughput of image acquisition (measurement (length measurement)) in a charged particle beam system including a charged particle beam device and a computer system configured to control the charged particle beam device. The charged particle beam device includes an objective lens, a sample stage, and a backscattered electron detector that is disposed between the objective lens and the sample stage and that adjusts a focus of a charged particle beam with which a sample is irradiated. The computer system adjusts a value of an electric field on the sample in accordance with a change in a voltage applied to the backscattered electron detector.