PURPOSE: To obtain an image having a high contrast between a pattern being transparent for a visible light and the other part, on the occasion when an object of inspection whereon the pattern transparent for the visible light is formed is illuminated by an illuminating light, an image of the object is formed on a prescribed plane of observation and the object is observed.

CONSTITUTION: An infrared light is selected from a light of a light source 1 by a filter 2 and a pattern 6 of a transparent conductive film on a glass base 7 is illiminated vertically by this infrared light through the intermediary of a relay lens 3, a half mirror 4 and an objective lens 5. A reflected light from the pattern 6 forms an image of an object of inspection on an image- sensing element 8 via the objective lens 5 and the half mirror 4. Since the reflectance of the transparent conductive film for an infrared ray is high, an image having a high contrast between the part of the pattern 6 of the transparent conductive film and the part of the glass base 7 is obtained.