1. An eye movement measuring apparatus comprising: an image forming part configured to obtain data optically to form a fundus oculi image of an eye based on the obtained data; and an image analysis part configured to analyze the formed fundus oculi image to determine eye movement of the eye, wherein the image forming part includes a tomographic image forming part configured to obtain the data by scanning the fundus oculi optically to form a tomographic image of the fundus oculi based on the obtained data, wherein the image analysis part determines eye movement of the eye based on the formed tomographic image of the fundus oculi, and wherein the tomographic image forming part comprises: a light source; an interference light generating part configured to generate interference light by splitting light output from the light source into signal light directed toward the fundus oculi of an eye and reference light directed toward a reference object and by overlapping the signal light passed through the fundus oculi and the reference light passed through the reference object; a scanning part configured to scan an irradiation position of the signal light on the fundus oculi; and a detecting part configured to receive the generated interference light to output a detection signal as the data; and the tomographic image forming part forms a tomographic image of the fundus oculi along the scanning direction based on the detection signal corresponding to scanning of the signal light with the scanning part.