PURPOSE: A focal indicator is provided to visually confirm interference at an image sensor generated when lights reflected from an internal reflecting mirror and external reflecting mirror reaches to the image sensor using a display device electrically connected to the image sensor. CONSTITUTION: A focal indicator comprises a support plate(110) and spherical reflector(120). The supporting plate is arranged between an interferometer(20) and optical system when measuring a focal position and focal distance. The supporting plate can be moved to a direction being closed to or being far from the interferometer. The spherical reflector reflects lights irradiated from the interferometer.
