To provide a multiphoton laser microscopy for achieving depth of visual field resolution that is comparable to one brought about by confocal laser scanning microscope, and also for reducing toxicity of both photobleaching and light.

The laser microscope uses simultaneous absorption of three or more photons to cause molecular excitation in the target substance, yielding intrinsic three-dimensional resolution. Phosphors, containing absorption of a single photon in short-wavelength band, are excited by strongly-imaged pulse on the sub-picosecond time scale from laser beam of relatively longer wavelength band. The phosphors absorb a fraction of approximately 1/3, 1/4 or even smaller than these, in order to create fluorescent images of a live cell and other ultramicroscopic objects. Fluorescence emission form the phosphors increases per three-, four- or higher dimensional power law, together with excitation intensity, and then makes the laser beam image, to limit not only photobleaching but also the fluorescence light to the vicinity of the focal plane.