An overcharge prevention device of a battery is provided and includes a safety fuse which is connected to a battery and a safety circuit which is connected in parallel to the battery and the safety fuse and includes a short-circuit switch which is disposed adjacent to a side in which the battery is swelled. The short-circuit switch is opened in a normal state, and short-circuits when the switch is pressurized due to the swelling of the battery to form a closed circuit with the battery and the safety fuse.