The effect of extremely low frequency (ELF) electromagnetic field (EMF) (50 Hz 0.5 mT) on the activity of alpha amylase (EC 3.2.1.1) was studied. In addition factors effecting the enzyme activity, temperature, pH, substrate concentration were also investigated. Our results show there is an increase in the enzyme activity when it is exposed to ELF EMF and also the velocity of the reaction increases. But there is no significant effect on optimal temperature and pH under the presence of the electromagnetic field.