A detection apparatus includes at least one processing unit, a light guide optical system configured to focus projected light to a spatial image forming plane to form an image thereon, and a sensor configured to shine a laser beam over a set scanning range to detect an entry depth of a target object in a direction orthogonal to the spatial image forming plane and an entry position of the target object on the spatial image forming plane, and the processing unit executes an operation associated with the entry position when the entry depth of the target object reaches a set depth. A display mode of a pointer image is displayed as superimposed on the spatial image forming plane is caused to change step by step in accordance with the entry depth of the target object in a direction orthogonal to the image forming plane which is detected by the sensor.