A charged-particle beam instrument is offered which can inspect side and rear surfaces of a sample. Two electron optical microscope columns are mounted in a vacuum chamber. Each of the microscope columns has an electron gun, a condenser lens system, a deflector, and a secondary electron detector. A sample stage assembly on which a sample is placed is mounted in the vacuum chamber. The stage assembly consists of a rotary stage, an X-stage, and a Y-stage. One of the microscope columns is placed in a position where the electron beam from the column can scan at least an upper part of a side surface of the sample. The other microscope column is placed in a position where the beam from the column can scan at least a lower part of the side surface of the sample.