Abstract: A high resolution optical microscope consists of an irradiation spot beam-forming mask which is disposed in a dark or a bright field, whereby a diameter of each of a plurality of irradiation spot beams onto an object to be measured is made smaller than a size of the object, beyond Rayleigh's resolution limit. In the irradiation spot beam-forming mask, a phase array is regularly disposed in a two-dimensional direction so that neighboring portions of each of the irradiation spot beams are optically phase-shifted from one another at 180.degree.. Thus, a wide observation surface and a prompt measurement can be performed with a high resolution of 0.1 .mu.m or less, far beyond Rayleigh's resolution limit.