A mobile device having an overcurrent cutoff function. In a mobile device having at least one function module, the mobile device includes a main power supply which supplies power to the mobile device, a power detection unit which detects whether power from the main power supply to the mobile device is cut off, and generates a power cutoff signal when the power is cut off, a backup power supply unit which supplies a backup power to the mobile device when the power from the main power supply to the mobile device is cut off, and a control unit which converts potential levels of the data lines and control signal lines between the control unit and the function module to a predetermined potential level in response to the power cutoff signal. Such a mobile device can minimize the consumption of the backup battery built into the mobile device when the main battery supplying main power to the mobile device is detached from the mobile device, to thereby extend the time for preserving data stored in the mobile device due to the minimized consumption of the backup battery.