To properly display pop-up displays showing announcement of calls and pop-up displays showing site restoration waiting states when there are too many pop-up displays to display.

When the number of the pop-up displays showing announcement of calls and the pop-up displays showing the site restoration waiting states exceeds a first predetermined number, the pop-up displays showing announcement of calls are displayed in an upper part of a display by a second predetermined number smaller than the first predetermined number, and the pop-up displays showing the site restoration waiting states are displayed in a lower part of the display by a number obtained by subtracting the second predetermined number from the first predetermined number. As for those exceeding the first predetermined number, only the existence of such pop-up displays is displayed. Thus, since both the pop-up displays are displayed while preferentially displaying the pop-up displays showing announcement of calls in the upper part, both can be properly displayed.