Provided is an electronic device. The electronic device includes: a main body mounted with an electronic unit including a controller, including a bezel disposed at the outer side thereof, and having a locking groove formed in the bezel; and a band part mounted with an additional device for exchanging an electric signal with the electronic unit and an electronic part providing information related to the additional device for the electronic unit, and including a coupling part detachably coupled to the locking groove. Here, the controller switches an operation mode of the main body according to the information related to the additional device provided by the electronic part when the main body and the band part are coupled to each other. Thus, when the band part mounted with the additional device is connected to the main body, the operation mode of the main body is automatically switched to a mode corresponding to the additional device, thereby providing convenience of use.