To provide, in observation of a sample that requires a movement between various devices, a charged particle beam device, a method for processing the sample, and an observation method which facilitate the movement between the devices. The charged particle beam device that processes an observation target on the sample using a charged particle beam includes: a sample stage on which the sample is placed; an observation unit configured to observe the observation target; and a writing unit configured to write information of the observation target in a writing position of the sample.