A photographic lens system for forming an object image is placed in the lens barrel of an electronic camera. In a camera body, a beam splitter for forming branched optical paths and an image sensing element for photoelectrically converting the formed object image are arranged. The beam splitter and the image sensing element are attached and disposed in the outer casing by a holding frame structure. The photographic lens system is attached and disposed in the lens barrel, which has a heat-radiating barrel made of aluminum. A heat-transfer path from the image sensing element to the heat-radiating barrel is formed by a back plate and a prism frame both made of aluminum, which are part of the holding frame structure.