There is provided a compact charged particle beam apparatus with a non-evaporable getter pump which maintains high vacuum even during emission of an electron beam without generating foreign particles. The apparatus comprises: a charged particle source; a charged particle optics which focuses a charged particle beam emitted from the charged particle source on a sample and performs scanning; and means of vacuum pumping which evacuates the charged particle optics. The means of vacuum pumping has a differential pumping structure with two or more vacuum chambers connected through an opening in series. A pump made of non-evaporable getter alloy is placed in an upstream vacuum chamber with a high degree of vacuum, and a gas absorbing surface of the non-evaporable getter alloy is fixed without contact with another part.