An apparatus has an optical member having a boundary surface on which light is incident, the optical member being adapted to transmit light entering the boundary surface from one side and to reflect light entering the boundary surface from the other side; a light source that emits light toward the optical member and irradiates light outgoing from the optical member onto a moving body; a camera that photographs via the optical member an image of light reflected from a reflection marker provided on a surface of the moving body; and a computation portion that computes movement information for the moving body based on the image of the light reflected by the reflection marker and photographed by the camera. An outgoing angle of the light outgoing from the boundary surface substantially coincides with an incoming angle at which the light reflected by the reflection marker enters the boundary surface.