To obtain a method and a device for measuring the fine structure of a material by a scanning laser microscope.

As to a microscope objective lens 2, the laser beam 4 of fundamental frequency W whose pulse is short and whose intensity is high is converged to a focal point 6 inside a specimen 8, and the third higher harmonics TH of frequency 3W are produced at the point 6. The third higher harmonics are condensed by a condenser lens 10, transmitted through a filter 12, so that the trace of an original beam being the basic frequency W is removed to be finally detected. The specimen 8 is scanned by moving the laser beam in an (x) direction and/or a (y) direction and/or a (z) direction (that is, along the specimen and/or crossing with the surface of the specimen and/or transmitted through the specimen) and by the irradiation of a laser beam. A third higher harmonic signal from all scanning parts is electrically collected in order to form an image.