A terminal set comprising: a main body having a first display and an inclination sensor configured to sense an inclination of the main body, wherein in a case in which the inclination sensor senses a vertical upper axis of the main body being inclined forward by 25 degrees or more or rearward by 60 degrees or more with respect to a vertical axis of a ground the main body is in a screen rotation nonactivation range where an automatic screen rotation to a horizontal mode or vertical mode is not performed; a terminal auxiliary device having a terminal case and a display case configured to rotate with respect to one another between a folded position and an unfolded position, wherein the terminal case forms a seating area configured to fasten the main body to the terminal auxiliary device, and wherein the display case includes a second display; and a controller configured to execute an application and output an execution screen of the application on the first display or the second display, wherein the controller is further configured to: receive a new output signal regarding a first application, the new output signal specifying the first application and including information of a display (151, 261) to output the execution screen of the first application, if the new output signal regarding the first application is received in a state in which the sensed inclination of the main body is within the screen rotation nonactivation range, retrieve an output rotation value allocated to the first display and an output rotation value allocated to the second display, and if at least one of the output rotation values corresponds to a horizontal mode, output the first application in the horizontal mode. a main body having a first display and an inclination sensor configured to sense an inclination of the main body, wherein in a case in which the inclination sensor senses a vertical upper axis of the main body being inclined forward by 25 degrees or more or rearward by 60 degrees or more with respect to a vertical axis of a ground the main body is in a screen rotation nonactivation range where an automatic screen rotation to a horizontal mode or vertical mode is not performed; a terminal auxiliary device having a terminal case and a display case configured to rotate with respect to one another between a folded position and an unfolded position, wherein the terminal case forms a seating area configured to fasten the main body to the terminal auxiliary device, and wherein the display case includes a second display; and a controller configured to execute an application and output an execution screen of the application on the first display or the second display, wherein the controller is further configured to: receive a new output signal regarding a first application, the new output signal specifying the first application and including information of a display (151, 261) to output the execution screen of the first application, if the new output signal regarding the first application is received in a state in which the sensed inclination of the main body is within the screen rotation nonactivation range, retrieve an output rotation value allocated to the first display and an output rotation value allocated to the second display, and if at least one of the output rotation values corresponds to a horizontal mode, output the first application in the horizontal mode. receive a new output signal regarding a first application, the new output signal specifying the first application and including information of a display (151, 261) to output the execution screen of the first application, if the new output signal regarding the first application is received in a state in which the sensed inclination of the main body is within the screen rotation nonactivation range, retrieve an output rotation value allocated to the first display and an output rotation value allocated to the second display, and if at least one of the output rotation values corresponds to a horizontal mode, output the first application in the horizontal mode.