A microscope apparatus has an illumination optical system illuminating a sample with laser light from laser light sources. A fluorescence detection optical system detects fluorescence from the sample. Fluorescence cubes are interchangeably provided in an optical path of the illumination optical system and lead the laser light to the sample. An objective lens is also provided. At least one of the fluorescence cubes includes an optical member that makes a principal ray of the laser light substantially parallel to an optical axis of the illumination optical system and concentrates the laser light on a given position that is on a pupil position of the objective lens and separated from the optical axis, thereby providing a microscope apparatus capable of changing from a confocal microscope to a total-internal-reflection fluorescence microscope by exchanging a fluorescence cube used in the fluorescence microscope.