A detection device includes: a display unit (101) an image capturing unit (102) that captures an image of a subject a gaze detection unit (354) that detects a gaze direction of the subject from a captured image captured with the image capturing unit (102) an output control unit (356) that displays, on the display unit (101), a diagnostic image which includes an image of a person including an image of a face and an image of a geometric pattern and a viewpoint detection unit (355) that, on the basis of the gaze direction, detects a first viewpoint which is a viewpoint of the subject in the image of the person and detects a second viewpoint which is a viewpoint of the subject in a region including at least one of a center of the geometric pattern, a characteristic part of the geometric pattern, a part of the geometric pattern in which lines depicting the geometric pattern are denser than in other parts, and a part of the geometric pattern where the geometric pattern changes in the image of the geometric pattern.
