In a laser scanning microscope comprising an infrared pulse laser; an objective lens focusing an infrared light from the infrared pulse laser on a sample; a condenser lens disposed on an opposite side of the objective lens across the sample for collecting an observation light that is generated by a nonlinear optical effect and has a wavelength shorter than a wavelength of the infrared light; a visible light detector detecting the observation light collected by the condenser lens, an IR partial transmission filter having partially-modified transmission characteristics for the infrared light is disposed near a front focal position of the condenser lens, and an infrared light detector detecting, through the IR partial transmission filter, a transmitted light from the sample collected by the condenser lens, is provided.