An UI device includes a display unit, a cancel button, an execution button, and print data selection buttons. Identification information of print data during printing is displayed on the display unit, and when the cancel button is pressed for a predetermined time, the print data during printing is canceled. Further, when the pressed time is less than the predetermined time, a list of identification information of the print data is shown so that one of print data can be selected with the print data selection buttons and the selection to cancel is determined with the execution button, thereby canceling the print data.