A charged particle beam apparatus covering a wide range of detection angles of charged particles emitted from a sample includes an objective lens for converging charged particle beams emitted from a charged particle source and a detector for detecting charged particles emitted from a sample. The objective lens includes inner and outer magnetic paths which are formed so as to enclose a coil. A first inner magnetic path is disposed at a position opposite to an optical axis of the charged particle beams. A second inner magnetic path, formed at a slant with respect to the optical axis of the charged particle beams, includes a leading end. A detection surface of the detector is disposed at the outer side from a virtual straight line that passes through the leading end and that is parallel to the optical axis of the charged particle beams.