An electronic device has a voltage converter configured to convert output voltage of a battery for supplying power for operating an electronic device into a preset voltage for output, a constant current load unit configured to receive the voltage output by the voltage converter and output a preset constant current, a battery voltage detector configured to detect the output voltage of the battery, and a remaining charge calculator configured to calculate the remaining charge of the battery based on a first battery voltage obtained by the battery voltage detector when operation of the constant current load unit is stopped and a second battery voltage obtained by the battery voltage detector when the constant current load unit is operating.