A display device capable of informing a user of a plurality of condition information items correctly even if a display area is restricted. A determination unit determines whether a plurality of conditions should be displayed on a display unit. A first display unit displays the condition information items showing the respective conditions to be displayed in turn in contracted messages, which are created by contracting the respective condition information items so as to be fitted within a display area of the display unit, when the determination unit determines that the plurality of conditions should be displayed. A second display unit displays the condition information item showing the condition to be displayed in a detailed message, which does not contract the condition information item, when the determination unit determines that one condition should be displayed.