An arbitrary entire region of a specimen, or a plurality of individual regions, is simultaneously stimulated without a time lag, or a strong stimulus is applied to an arbitrary region of a specimen. The invention provides a microscope apparatus including a first stimulation optical system having a galvanometer mirror that scans a specimen with first stimulus light, which applies an optical stimulus to a specimen, on the specimen; a second stimulation optical system which has a plurality of two-dimensionally arrayed movable mirrors and which switches the angle of each movable mirror so that second stimulus light, which applies an optical stimulus to the specimen, can be selectively deflected towards the specimen; and a dichroic mirror that combines a light path of the first stimulation optical system and a light path of the second stimulation optical system.