To provide an external opening locking structure which has a compact external dimension, and is difficult to grasp the structure from outside, to thereby makes it difficult to break the lock.

The external opening locking structure for locking a fitting which is openably mounted in a peripheral frame 1, is comprised of a driving unit 3 and a control unit 4. The driving unit is arranged in the peripheral frame 1 and has a bolt piece 7 for implementing locking/unlocking of a bolt bearing portion of the fitting. The control unit 4 is arranged at a location separate from the driving unit 3, and functions to receive a remote control signal and to transmit an activating signal of locking/unlocking to the driving unit 3. Further the external opening locking structure is comprised of a power source unit 5 for feeding normal rated power to the driving unit 3 and the control unit 4, which is separately arranged from the driving unit and the control unit. The power source unit 5 has an emergency battery for use in an emergency in place of a commercial power source, and a power source switching section for switching from the commercial power source to the emergency battery.