An object of the invention is to provide a charged particle beam apparatus capable of performing high-precision measurement even on a pattern in which a width of edges is narrow and inherent peaks of the edges cannot be easily detected. In order to achieve the above object, there is proposed a charged particle beam apparatus including an opening portion forming member having a passage opening of a charged particle beam and a detector for detecting charged particles emitted from a sample or charged particles generated by causing the charged particles to collide with the opening portion forming member, the charged particle beam apparatus including: a deflector for deflecting the charged particles emitted from the sample; and a control device for controlling the deflector, the control device performing pattern measurement with the use of a first detected signal in which a signal of one edge is emphasized relatively more than a signal of another edge among a plurality of edges on the sample and a second detected signal in which the signal of the another edge is emphasized relatively more than the signal of the one edge among the plurality of edges.