An optional apparatus of an image forming device is provided for setting its own driving condition using received specification information of a main body and method thereof. The optional apparatus is additionally combined into the main body of the image forming device to expand functions of the image forming device, and includes a driving unit driven to perform an addition function required to expand the functions of the image forming device, and a control unit for receiving specification information of the main body, setting a driving condition of the driving unit based on the received specification information, and then controlling the driving unit according to the set driving condition. The optional apparatus can be implemented as a general optional apparatus that can be combined into any kind of image forming device.