In an ophthalmic operation microscope, an illumination optical system illuminates a patient's eye with illumination light. An observation optical system is used for observing the patient's eye illuminated. An objective lens is disposed in an observation optical path. An interference optical system splits light from a light source into measurement light and reference light, and detects interference light generated from returning light of the measurement light from the patient's eye and the reference light. A first lens group is disposed between the light source and the patient's eye in an optical path of the measurement light. A second lens group is disposed between the first lens group and the patient's eye in the optical path of the measurement light. A deflection member is disposed between the first lens group and the second lens group in the optical path of the measurement light.