To provide a technology for detecting a slight misregistration, which can be applied to tracking for a moving image. An ophthalmologic apparatus includes an optical system, a rotational movement amount calculator, a registration unit, a parallel movement amount calculator, a driver, and a controller. The optical system is used to capture a moving image of a subjects eye. The rotational movement amount calculator calculates a rotational movement amount between a first image and a second image included in the moving image acquired by the optical system. The registration unit performs registration between the first image and the second image in the rotation direction based on the rotational movement amount calculated by the rotational movement amount calculator. The parallel movement amount calculator performs a phase only correlation process on the first image and the second image registered by the registration unit to calculate a parallel movement amount between the first image and the second image. The driver moves the optical system. The controller controls the driver based on the parallel movement amount calculated by the parallel movement amount calculator.
