PURPOSE: To prevent the confirmation operation of a time sequential alarm display by being disturbed by newly generated alarms.

CONSTITUTION: When the new alarms n-1 and n-2 are generated while confirming the time sequential alarms a-1, a-2,... and a-16 on the screen of a page 1/n in a figure (A), the alarm display contents of the present display screen are not changed, only the page is changed to 2/n, the page display is reverse-displayed or flicker-displayed and the generation of the new alarms is informed as in the figure (B). The data of the new alarms are stored in the page 1/n. When the display screen is switched in this case, however, time sequential alarm data are edited again to a form for which the data are time sequentially blocked and arranged for the respective pages as in the past and when the page 1/n is switched and displayed for instance, the screen in which the alarms a-1-a-14 succeed the new alarms n-1 and n-2 of the screen of the page 1/n in the (B) is displayed.