A distortion in an image, which occurs when the image is formed by scanning a retina with a resonance scanner, is reduced. An image forming apparatus for forming an image of an object to be inspected includes: a detecting unit for detecting signals relating to a resonance scanner which is set to scan the object to be inspected with measurement light at a first frequency； a determining unit for determining a second frequency which is estimated to be used for the scanning by the resonance scanner, based on a correlation between groups of the detected signals for each cycle of the first frequency； and an image forming unit for forming the image of the object to be inspected based on the determined second frequency.
