A confocal optical scanner of Nipkow disk type for measuring a sample, in which each component of two or more color pigments, has a high reflection mirror for separating an excited light to be radiated onto the sample and a fluorescence emitted from the sample, wherein a reflectance of the high reflection mirror is from 80% to 100% in a measured wavelength region including at least an excited light wavelength region and a fluorescence wavelength region. Thereby, the confocal optical scanner capable of measuring a polychromatic fluorescent image at the same time is realized with the enhanced light receiving efficiency of fluorescence, using one high reflection mirror without using a plurality of dichroic mirrors by exchange.