To suppress sudden changes in brightness due to a disturbance in a captured image, provided is a medical observation device, including: an acquisition section that acquires a sensing result of a brightness of an image of a subject in a living organism; and a control section that decides, according to a first interval in which the brightness sensing result indicates a value inside a certain range, a second interval in which to maintain an exposure of an imaging section at an exposure corresponding to a value included in the range.