Methods and apparatuses for transmitting data to an external device are provided. The method includes establishing a communication link with the external device by using a first application, and displaying a first window that corresponds to the first application, in response to an execution request for a second application that is different from the first application, displaying a second window that corresponds to the second application as a background of the first window, receiving a sharing mode request via the first window, and in response to the sharing mode request, setting an operation mode of the device as a sharing mode, and transmitting data that is provided from the second application to the external device via the communication link.