The present invention relates to a lens-less Foucault method wherein a transmission electron microscope objective lens (5) is turned off, an electron beam crossover (11, 13) is matched with a selected area aperture (65), and the focal distance of a first imaging lens (61) can be changed to enable switching between a sample image observation mode and a sample diffraction pattern observation mode, characterized in that a deflector (81) is disposed in a stage following the first imaging lens (61), and conditions for an irradiating optical system (4) can be fixed after conditions for the imaging optical system have been determined. This allows a lens-less Foucault method to be implemented in a common general-use transmission electron microscope with no magnetic shielding lens equipped, without burdening the operator.