An electronic flash device, detachably attached to a photographic camera, comprising a circuitry for carrying out preparatory operation for a flash photography, an input section for receiving a first start signal from the photographic camera and for outputting the same, signal outputting means responsive to a manual operation for outputting a second start signal, and power supply hold means connected to the circuitry, the input section and to the operational member. The above power supply hold means includes a power supply start section for starting the power supply to the circuitry by receiving either of the start signals, a power supply stop section for stopping the power supply to the circuitry when a predetermined time period has passed since the power supply start section starts the power supply, a judging section for judging by which start signal the circuitry is started and a changing section for changing the predetermined power supply time period in response to the judged result of the judging section such that the predetermined time period set when the circuitry is started by the first start signal is shorter than the predetermined time period set when the circuitry is started by the second start signal.