A data communication device that can communicate with an external device includes a scanner, a log-in processing unit, a sending unit, and a log-out processing unit. The scanner inputs image data. The log-in processing unit enables a user to log in to the data communication device. The user who logs in to the data communication device can submit an instruction to send image data input by the scanner to the external device. The sending unit sends the image data input by the scanner to the external device. The log-out processing unit enables the user to log out of the data communication device even if sending of the image data is not completed. Even if the user logs out of the data communication device after the user has submitted the instruction and before sending of the image data is completed, the sending unit continues the sending of the image data.