Thermal desorption of Ar implanted with energies 150 keV and 100 keV with fluence 1×10^16 cm^-2 into GaAs is considered. A sudden release of Ar is observed in temperature range 1100 -1180 K as a single narrow peak in TDS (Thermal Desorption Spectroscopy) spectra. This is accompanied by a strong background signal from atmospheric Ar trapped in various parts of the spectrometer. Desorption peak shift analysis allows estimation of desorption activation energy values - these are 3.6 eV and 2.5 eV for implantation energies 150 keV and 100 keV, respectively. These results are comparable to that measured for Ar implanted into germanium target.