To provide an alarm device sounding an alarm in the alarm device for a fire extinguisher, mounted to the fire extinguisher.

The alarm device for the fire extinguisher includes an alarm box (2) provided at a circular adjustable band (1); a cover (3) for the alarm box (2); a Velcro (R) tape loop (8) provided at the upper part of the alarm box (2); a buzzer (4) provided in the alarm box (2); a battery (5) serving as a power source; a magnet sensor (a switch part) (6); and a magnet sensor (a switch part) (7) for inspection. The end of a mounting plate (9) is provided with a magnet sensor (a magnet part) (10), and the other end is provided with an adjustable hole (11). A magnet sensor (the magnet part) (12) for inspection is provided with a Velcro (R) tape hook (13).