Provided is an electric device, power device, electric device system, and management device capable of providing a theft prevention function that requires less effort as compared to the prior art. A power tool comprises a main power tool unit, and a battery pack 4 which can be attached to and removed from the main power tool unit. The main power tool unit and the battery pack each have a storage means for storing at least one authentication code and a communication means for transmitting and receiving the authentication code, and permit use when an authentication code received via the communication means matches at least one of the authentication codes stored in the storage means, and do not permit use when said authentication code does not match any of the authentication codes. The authentication code is set by a management device which is an external device.