The general purpose spherical nonmagnetic detector (SND) is now taking data at VEPP-2M \(e^+e^-\) collider in BINP (Novosibirsk) in the centre of mass energy range of \(0.2 \div 1.4\) GeV. The energy calibration of the NaI(Tl) calorimeter of the SND detector with cosmic muons is described. Using this method, the energy resolution of \(5.5 % (\sigma)\) for 500 MeV photons was achieved.