Provided is a microscope provided with: a scanner that scans an excitation beam coming from a light source; an objective optical system that focuses the scanned excitation beam onto a sample and that collects fluorescence generated at individual scanning positions in the sample; a detector that detects the collected fluorescence; a light blocking member that is disposed between the detector and the system and that partially blocks the collected fluorescence; a switching portion that switches the positional relationship between the member and a light-focusing point of the excitation beam in the sample between an optically conjugate positional relationship, in which an in-focus fluorescence generated at the light-focusing point passes through the member, and a non-conjugate positional relationship, in which the in-focus fluorescence is blocked by the member; and a computing portion that computes a difference between fluorescence signals acquired by the detector in the two positional relationships.