A transparent light-guiding unit for guiding imaging light, a positioning portion provided at the transparent light-guiding unit, a camera for performing space detection of an external space, and a camera holder that contacts the positioning portion and is attached to the transparent light-guiding unit, and holds the camera are provided. In this case, the camera holder contacts the positioning portion, thus, when the camera is attached to the transparent light-guiding unit, high positional accuracy is reliably maintained.