A microscope includes a laser light source, a deflecting device, an objective lens, an irradiating system for irradiating a sample with laser light via the objective lens, a detecting device that detects fluorescence from a sample, and a collector lens unit insertable and removable in and out of the path of rays. When the collector lens unit is in the path, laser light converges on the pupil position of the objective lens decentered from the center of the pupil position of the objective lens with chief rays being substantially parallel with the optical axis, and, when the collector lens unit is out of the path, the laser light converges on and, via the deflecting device, scans the sample surface, to achieve a prompt switching between a laser scanning microscopy mode and a total internal reflection fluorescence microscopy mode at low cost.