A composite charged particle beams apparatus of the present invention allows a sample (5)'s cross-section or edge plane to be observed by using an electron beam (2b), the sample (5)'s cross-section or edge plane being fabricated by using an ion beam (1b). The radiation device includes a detector (7) which is capable of detecting low-loss back-scattered electrons (12) including elastically-scattered electrons (11), these electrons (12, 11) being induced by the electron beam (2b) with which the sample (5)'s cross-section or edge plane is irradiated. Moreover, it is desirable that the detector (7) be set up in a space outside an electron-beam column (2a). The above-described configuration has allowed implementation of the high-resolving-power and low-damage SEM observation of the surface information about material and composition of the sample's FIB-fabricated cross-section or edge plane. Furthermore, when detecting the low-loss back-scattered electrons (12), information about the different depths relative to the sample's surface has been also made available by selecting the energy bands of the detected electrons.