In the present invention, in a battery adapter to be engaged with a camera body, a tripod screw provided at an upper surface portion is engaged with a tripod screw of the camera body, and a positioning pin is fitted in a positioning hole provided in the camera body. Furthermore, a contact piece support including electrode contact portions is inserted into a battery chamber of the camera body in order to effect electrical connection with battery contact pieces provided in the battery chamber. A waterproofing seal for waterproofing the gap between the contact piece support and the battery chamber is provided around a lower portion of the contact piece support.