To obtain an image of high quality with a relatively low cost by constituting a confocal microscope so as to be able to scan a subject to be tested on at least one line of an axis while using a moving objective lens.

A part 12 of the radiated output 11 of a light source 1 is reflected at a beam splitter 3 and collimated in a lens 4. Next, part 12 of light beams 12a is focused by a movable objective lens 5 of low resonance and low mass which can be supported by a flexible material. When one part of a subject to be tested 7 enters into the focus 13 of the objective lens 5, a light beam 14 returns to the beam splitter 3 along beam paths 14, 14b and 14a. One part 14c of the light beam 14 irradiating the beam splitter 3 passes a lens 8 to be focused on pinhole openings 9. The quantity and the intensity of a light beam to be detected with a detector 10 are made to be related to a distance from the focus 13 on a beam axis to the reflecting part of the subject to be tested 7.