A corneal surgery apparatus, which comprises: - a laser source - a laser irradiation optical system capable of changing an irradiation position with a laser beam emitted from the laser sourceon a cornea of a patient's eye; - a visible fixation light on which the patient's eye is fixated during a surgical operation; and - an eye position change detection unit (18, 24, 25, 30) - which comprises an illumination optical system arranged to illuminate an anterior segment of the patient's eye with infrared illumination light; and - an image pick-up camera arranged to pick up an image of the anterior segment illuminated by the illumination optical system, the image pick-up camera being provided with an image pick-up element arranged to receive infrared light, - and which is arranged to detect movement of the patient's eye such that the irradiation position with the laser beam which is applied by the laser irradiation optical system tracks the movement of the patient's eye, and the cornea is ablated to a desired shape by the application of the laser beam with the tracking, characterized in that - the eye position change detection unit (18, 24, 25, 30) further comprises an image processing unit arranged to extract an iris pattern and a background of the iris pattern of an iris portion of the anterior-segment image by processing image signals from the image pick-up camera, and a control unit arranged to adjust at least one of a set value of an illumination light amount of the illumination optical system and a set value of a gain of the image pick-up camera such that a luminance difference between the iris pattern and the background of the iris pattern is maximized or exceeds a predetermined reference value and luminance at the iris portion is not saturated, detect the iris pattern, and detect the movement of the patient's eye based on the iris pattern. - a laser source - a laser irradiation optical system capable of changing an irradiation position with a laser beam emitted from the laser sourceon a cornea of a patient's eye; - a visible fixation light on which the patient's eye is fixated during a surgical operation; and - an eye position change detection unit (18, 24, 25, 30) - which comprises an illumination optical system arranged to illuminate an anterior segment of the patient's eye with infrared illumination light; and - an image pick-up camera arranged to pick up an image of the anterior segment illuminated by the illumination optical system, the image pick-up camera being provided with an image pick-up element arranged to receive infrared light, - and which is arranged to detect movement of the patient's eye such that the irradiation position with the laser beam which is applied by the laser irradiation optical system tracks the movement of the patient's eye, and the cornea is ablated to a desired shape by the application of the laser beam with the tracking, - which comprises an illumination optical system arranged to illuminate an anterior segment of the patient's eye with infrared illumination light; and - an image pick-up camera arranged to pick up an image of the anterior segment illuminated by the illumination optical system, the image pick-up camera being provided with an image pick-up element arranged to receive infrared light, - and which is arranged to detect movement of the patient's eye such that the irradiation position with the laser beam which is applied by the laser irradiation optical system tracks the movement of the patient's eye, and the cornea is ablated to a desired shape by the application of the laser beam with the tracking, - the eye position change detection unit (18, 24, 25, 30) further comprises an image processing unit arranged to extract an iris pattern and a background of the iris pattern of an iris portion of the anterior-segment image by processing image signals from the image pick-up camera, and a control unit arranged to adjust at least one of a set value of an illumination light amount of the illumination optical system and a set value of a gain of the image pick-up camera such that a luminance difference between the iris pattern and the background of the iris pattern is maximized or exceeds a predetermined reference value and luminance at the iris portion is not saturated, detect the iris pattern, and detect the movement of the patient's eye based on the iris pattern.