A manual unlocking structure arranged in a locking device for locking a power feeding plug to a power receiving connector arranged in a vehicle. The power feeding plug includes a hook. The locking device includes a fastening member capable of fastening the hook to the power receiving connector to lock the power feeding plug to the power receiving connector. The manual unlocking structure includes an operation member that is manually operable to move and separate the fastening member from the hook. A user operates the operation member to manually unlock the power feeding plug. An operation box is arranged in the vehicle and used to manually operate the operation member in the vehicle.