An ophthalmologic apparatus comprising: an optical system that includes an optical scanner, deflects light from a light source using the optical scanner, projects the light onto a subject's eye, and receives light based on returning light from the subject's eye; a movement mechanism that moves the subject's eye and the optical system relative to each other; an image acquisition unit that acquires an image of the subject's eye; an abnormality detector that detects abnormality based on a reference image and the image of the subject's eye acquired by the image acquisition unit; a scan controller that controls the optical scanner to re-perform a first scan or a second scan so as to project light from the light source onto a start position of the first scan, which is being performed for the subject's eye at an acquisition timing of the image of the subject's eye, or a start position of the second scan performed before the first scan, when the abnormality is detected by the abnormality detector; and a tracking controller that controls the movement mechanism so that the optical system follows a movement of the subject's eye based on the reference image and the image of the subject's eye, when the abnormality is not detected by the abnormality detector, wherein the image acquisition unit acquires an anterior segment image of the subject's eye, and the tracking controller controls the movement mechanism based on an amount of displacement of characteristic positions in the reference image and the anterior segment image, characterized in that the ophthalmologic apparatus further comprises: an alignment controller that controls the movement mechanism to perform position matching of the optical system with respect to the subject's eye, when the abnormality is detected, and that the scan controller re-performs the first scan or the second scan, after the position matching by the alignment controller is completed. an optical system that includes an optical scanner, deflects light from a light source using the optical scanner, projects the light onto a subject's eye, and receives light based on returning light from the subject's eye; a movement mechanism that moves the subject's eye and the optical system relative to each other; an image acquisition unit that acquires an image of the subject's eye; an abnormality detector that detects abnormality based on a reference image and the image of the subject's eye acquired by the image acquisition unit; a scan controller that controls the optical scanner to re-perform a first scan or a second scan so as to project light from the light source onto a start position of the first scan, which is being performed for the subject's eye at an acquisition timing of the image of the subject's eye, or a start position of the second scan performed before the first scan, when the abnormality is detected by the abnormality detector; and a tracking controller that controls the movement mechanism so that the optical system follows a movement of the subject's eye based on the reference image and the image of the subject's eye, when the abnormality is not detected by the abnormality detector, the image acquisition unit acquires an anterior segment image of the subject's eye, and the tracking controller controls the movement mechanism based on an amount of displacement of characteristic positions in the reference image and the anterior segment image, characterized in that the ophthalmologic apparatus further comprises: an alignment controller that controls the movement mechanism to perform position matching of the optical system with respect to the subject's eye, when the abnormality is detected, and that the scan controller re-performs the first scan or the second scan, after the position matching by the alignment controller is completed. an alignment controller that controls the movement mechanism to perform position matching of the optical system with respect to the subject's eye, when the abnormality is detected, and that the scan controller re-performs the first scan or the second scan, after the position matching by the alignment controller is completed.