The invention discloses an earthquake alarm, which is mainly characterized in that a hollow magnetic rod is hung in the air by a thin wire; the interior of the magnetic rod is provided with a laser transmitter; when the spot of laser hits on a CCD photoelectric sensor, the sensor senses the movement of the spot and is connected with a computer to record data on the computer; in normal condition, the magnet does not rotate, and the laser spot also does not move; the geomagnetic field changes severely a few minutes or hours before the earthquake to cause the magnetic rod to rotate slightly, thereby causing the position of the laser spot to offset, the offset is recorded in the computer by the CCD photoelectric sensor, if the offset is larger than a certain range, the computer alarms, and the range can be regulated by computer software. As the technical scheme in the invention is adopted, compared with the prior art, the earthquake alarm has the advantages of sensitive instrument, high precision, pure mechanical type, reliable work, and good ability of not being interfered by cell phone signals or thunder and lightening.