A data transmission device, configured to be connected with terminal devices via a network, includes an image acquiring unit configured to acquire image data, an identifying data acquiring unit configured to acquire user identifying data to identify a user of the data transmission device, a first file creating unit configured to create a first file that includes the image data acquired by the image acquiring unit, a second file creating unit configured to create a second file that includes the user identifying data acquired by the identifying data acquiring unit and data to specify the first file created by the first file creating unit, and a transmission unit configured to transmit the first file and the second file to a destination one of the terminal devices.