A compact and inexpensive multiphoton-excitation laser scanning microscope for observing fluorescence by multiphoton excitation having a plurality of wavelengths by irradiating a specimen with ultrashort pulsed laser light having a plurality of wavelengths is provided. A multiphoton-excitation laser scanning microscope includes a laser light source that emits ultrashort pulsed laser light with a single wavelength, an optical fiber into which the ultrashort pulsed laser light from the laser light source is introduced and which broadens the spectrum of the ultrashort pulsed laser light, a laser scanning unit that scans the spectrally broadened ultrashort pulsed laser light emitted from the optical fiber, an objective optical system that focuses the scanned ultrashort pulsed laser light onto a specimen, optical detectors that detect fluorescence by multiphoton excitation emitted from the focal position of the ultrashort pulsed laser light in the specimen, and a dispersion-compensating optical system that compensates for the group velocity dispersion of the entire microscope that influences the pulse width of the ultrashort pulsed laser light.