To attain the observation of only the minite object without reducing the resolution at the time of observing the minute object which is equal to or below the resolution through the dark field microscope.

Between a light source 21 and a sample 25, an aperture diaphragm 10 is arranged on the incident pupil position of a condenser lens 24. Light from the light source 21 is partly shielded by the aperture diaphragm 10. And also, a light shielding member 15 is arranged on the exit pupil position of an objective lens 26, and light passing by the objective lens side far away from zero-order diffracted light by the sample 25 among illuminating light is partly shielded by the light shielding member 15.