Abstract: A charged particle beam device includes a lens barrel having a charged particle source, a sample chamber in which a sample to be irradiated with a charged particle beam is provided, and a heat emission type electron source disposed in the sample chamber and maintained at a lower potential than that of an inner wall of the sample chamber, in which the inside of the sample chamber is cleaned by electrons (e?) emitted from the heat emission type electron source after a heating current is generated by applying a voltage from an electron source power supply. The heat emission type electron source is maintained at a lower potential than that of the inner wall of the sample chamber by applying a negative voltage to the heat emission type electron source using a bias power supply. A magnitude of the negative voltage applied to the heat emission type electron source is preferably about 30 to 1000 V, particularly preferably about 60 to 120 V.