Provided are a method and an apparatus for controlling an electronic device including a flash. The method includes obtaining light emission waveform data including light emission times and light emission intensities of the flash corresponding to a plurality of pre-set guide numbers. Also, calculating a waveform area of the light emission waveform data and calculating light emission amounts regarding the respective guide numbers by using the waveform area. The method further includes calculating a main guide number corresponding to light emission amount that satisfies necessary light emission amounts obtained when the flash pre-flashes from among the respective light emission amounts and controlling the flash to emit light according to a light emission time and light emission intensity based on the calculated main guide number.