A power cable adaptor includes a casing that has a receiving space, a retaining sleeve disposed in the casing and conductive members disposed within the retaining sleeve. The conductive members respectively define conductive channels. A cap is detachably connected to the casing and covers the receiving space. A wire dispenser is detachably received in the receiving space. The cap has an opening communicating with the conductive channels through the receiving space. The wire dispenser has wire passages communicating with the conductive channels and the opening of the cap.