Multiphoton excitation laser scanning microscope and multiphoton excitation fluorescence image acquiring method

A multiphoton-excitation laser scanning microscope capable of efficiently collecting fluorescence emitted from a specimen to acquire a brighter multiphoton-excitation fluorescence image is provided. This multiphoton-excitation laser scanning microscope includes a multiphoton-excitation laser light source for emitting ultrashort pulsed laser light, a light-scanning unit configured to scan a specimen with the ultrashort pulsed laser light emitted from the multiphoton-excitation laser light source in two dimensions, an objective lens configured to focus the ultrashort pulsed laser light scanned by the light-scanning unit on the specimen, a collector lens disposed opposite the objective lens, with the light-scanning unit disposed therebetween, to collect fluorescence emitted from the specimen, and a light detector configured to detect the fluorescence collected by the collector lens. The collector lens has a higher numerical aperture and a larger field number than the objective lens.