An earthquake is an unpredictable natural disaster that causes damage to lives and property. It happens suddenly and we cannot stop it but we can be alerted from it. In today’s time, there are many technologies which can be used to detect the small shakes and knocks, so that we can take precautions prior to some major vibrations in earth. Here we are using Accelerometer to detect the pre-earthquake vibrations. Accelerometer ADXL335 is highly sensitive to shakes and vibrations along with all the three axes. Here we are building an Arduino based Earthquake Detector using Accelerometer.