Provided is a USB port locking device including: a blocking member having a blocking coupling part to block access of an external device; an external USB port part connected to the blocking member and to which an external USB connection port is insertively coupled; a signal connection part enabling signal transmission between a terminal inside the USB port of the electronic device and the external USB connecting port; a locking member selectively locked to the electronic device so that the blocking member is not forcedly removed; a stopping member selectively blocking an unauthorized external USB connecting port from being inserted into the external USB port part; and a lock member controlling a locking operation of the locking member and a blocking operation of the stopping member by interfering with the locking member and the stopping member when they are inserted into the blocking member.