A light-projecting device comprises an ocular optical system facing an emergent opening of a hollow pentagonal mirror. A superimpose-plate is provided in an incident opening of the hollow pentagonal mirror so that a subject image obtained through a photographing optical system is formed. The superimpose-plate is put on a focusing glass. A mark, indicated in a picture plane of the view finder, is formed on the superimpose-plate. A light source radiates an illumination light beam. A light-projecting prism reflects the illumination light beam toward the emergent opening. The light-projecting prism has a light-projecting plane. The light-projecting plane is located below the optical axis of the ocular optical system.