A microprocessor unit of a communication terminal device determines whether or not a destination terminal is a communication terminal manufactured by a same manufacturer as the communication terminal device in accordance with a manufacturer code transmitted from the destination terminal. A display unit displays a message to notify a determination result to a transmitter and to urge the transmitter to perform a selection operation for executing or canceling a transmission of image data. When the transmitter selects a function key displayed on the display unit in accordance with the message, the microprocessor unit executes or cancels the transmission of the image data.