1. A fundus image acquiring apparatus, comprising: a first fundus image acquiring unit configured to acquire, at a first frame rate, a first fundus image including at least one fundus image of an eye to be inspected; an extraction unit configured to extract a characteristic image including a characteristic point from the acquired first fundus image; an evaluation unit configured to evaluate luminance of the characteristic image for detecting a movement of the eye to be inspected; a determination unit configured to determine a second frame rate based on a result of the evaluation by the evaluation unit; a second fundus image acquiring unit configured to acquire, at the second frame rate, a second fundus image including the characteristic point, wherein luminance of the acquired second fundus image is different from luminance of the acquired first fundus image; and a detection unit configured to detect the movement of the eye to be inspected based on the acquired second fundus image, wherein the determination unit determines the second frame rate on the basis of a luminance difference between luminance information of each of a plurality of divided areas in the extracted characteristic image, wherein the first fundus image acquiring unit uses an image sensor to acquire the first fundus image, wherein the second fundus image acquiring unit uses an image sensor to acquire the second fundus image, and wherein the extraction unit, the evaluation unit, the determination unit, and the detection unit are implemented using a processor.