An autostereoscopic projection device comprises a light source providing a light, a light scanning module, a light transmitting module, a light combining module including a first light combining element, a spatial light modulator module including a first spatial light modulator element, and a lens. The light scanning module includes a reflective surface and an actuating device capable of deflecting the reflective surface. The normal vector of an incident surface of the first light combining element is coplanar with the normal vector of a reflective surface of the first spatial light modulator element, and the coplanar plane is perpendicular to a disposition plane of the projection device. The light provided by the light source module is transmitted through the light scanning module, the light transmitting module, the light combining module and the spatial light modulator module sequentially and then leaves the projection device through the lens.