An ink jet printer is provided with an ink jet head that executes a printing action in which ink is discharged toward a print medium, a transportation device that transports the print medium, and a controller that controls the ink jet head to execute the printing action. The controller controls the ink jet head to execute the printing action when the ink jet printer has finished receiving a predetermined amount of print data. In a case where a time since a last printing action has exceeded a predetermined time, the controller prevents the ink jet head from executing the printing action against a partially printed print medium, and controls the transportation device to eject the print medium.