To enable switching of at least two of the observation methods in an optical microscope system for e.g. bright field observation, dark field observation, and differential interference observation.

A confocal laser scanning microscope for acquiring a confocal image of a sample includes: a laser optical system which acquires a confocal image of the sample; an optical microscope optical system which detects measurement light from the sample to acquire a non-confocal image of the sample; a first field lens arranged in the optical microscope optical system; and a second field lens arranged in the laser optical system. The first and second field lenses shorten back focal lengths for forming the non-confocal image and confocal image.