To automatically lock a shutter when the shutter is closed without providing an electric wire on a shutter side.

In this automatic locking device, an electric lock 37 is provided in a recessed part 11 on a floor 9 so that a latch 39 comes in and out below a hook 15 provided below a fixed bar 13. A detector 41 detecting that a shutter 3 is closed and an unlocking signal input part 45 inputting an unlock signal when the shutter 3 is opened are provided on the floor 9 or a wall. The electric lock 37 protrudes the latch 39 when a detection signal from the detector 41 is input to prevent the rotation of the hook 15 and pulls the latch 39 in when the unlocking signal is input from the unlocking signal input part 45 to allow the rotation of the hook 15.