1. A detection apparatus comprising: a display; an imaging unit configured to image a subject; an eye gaze detector configured to detect an eye gaze direction of the subject based on a captured image captured by the imaging unit; an output controller configured to display a diagnostic image that includes a person image and a geometric pattern image, onto the display; and a gaze point detector configured to detect a first gaze point as a gaze point of the subject in the person image based on the eye gaze direction, and configured to detect a second gaze point as a gaze point of the subject in a region that includes at least one of a center of a geometric pattern, a characteristic portion of the geometric pattern, a portion in which density of lines forming the geometric pattern is higher than other portions, and a portion in which the geometric pattern changes, in the geometric pattern image.