  We have developed MICROMEGAS (MICRO MEsh GASeous) detectors for detecting
{\alpha} particles emitted from an 241-Am standard source. The voltage applied
to the ionization region of the detector is optimized for stable operation at
room temperature and atmospheric pressure. The energy of {\alpha} particles
from the 241-Am source can be varied by changing the flight path of the
{\alpha} particle from the 241 Am source. The channel numbers of the
experimentally-measured pulse peak positions for different energies of the
{\alpha} particles are associated with the energies deposited by the alpha
particles in the ionization region of the detector as calculated by using
GEANT4 simulations; thus, the energy calibration of the MICROMEGAS detector for
{\alpha} particles is done. For the energy calibration, the thickness of the
ionization region is adjusted so that {\alpha} particles may completely stop in
the ionization region and their kinetic energies are fully deposited in the
region. The efficiency of our MICROMEGAS detector for {\alpha} particles under
the present conditions is found to be ~ 97.3 %.
