The present invention is directed to a battery residual quantity display method for performing display of battery residual quantity of a battery pack mounted at an electronic equipment and serving to supply power to the electronic equipment. When power is turned ON, a first microcomputer (3) of the camera body (1) side serves to first acquire, by serial communication, information for battery residual quantity display from a second microcomputer (7) of the battery pack (2) side loaded at the camera body to perform battery residual quantity display on the basis of the acquired information to subsequently acquire, by serial communication, information for authentication processing from the second microcomputer of the battery pack side to perform an authentication processing for judging on the basis of the acquired information as to whether or not the battery pack connected to the camera body is genuine battery pack to update, after the authentication processing, the content of the battery residual quantity display on the basis of information for battery residual quantity display acquired by serial communication from the microcomputer of the battery pack side.