In order to provide a charged particle beam apparatus that can detect charged particle beam signals in discrimination into a plurality of energy bands, and obtain high-resolution images for each of the energy bands using the signals, the charged particle beam apparatus has a charged particle source (12-1); an aperture (16) that limits the diameter of the charged particle beam (4); optics (14, 17, 19) for the charged particle beam; a specimen holder (21); a charged particle detector (40) that detects secondary charged particles and reflected charged particles from a specimen; and signal calculation unit that processes the output signal from the charged particle detector. The charged particle detector (40) is provided with a first small detector (51) having a first detection sensitivity and a second small detector (52) having a second detection sensitivity, and makes the detection solid angle viewed from a position on the specimen, to which the charged particle beam (4) is to be radiated, to be the same for the first small detector (51) and the second small detector (52).