A USB lock for an electronic device may comprise an inner casing, an outer casing, a USB connector and a driving unit. The inner casing has a front opening to secure the USB connector thereon. A rear portion of the inner casing has a tube body, and a first through hole penetrating through the tube body is communicated with the front opening and configured to receive the driving unit with a lock rod and a key lock. The USB lock of the present invention is configured to engage with a USB port of a 3C product to achieve the anti-theft effect, which is easily to assembly, simplifies the structure, lowers manufacturing cost and prevents the 3C product from getting infected with a virus through an unsafe USB.