A new method to grow stress‐free GaAs on bent Si substrates is proposed and demonstrated by metalorganic chemical vapor deposition. The stress produced by the thermal expansion coefficient difference of Si and GaAs is compensated by the external mechanical strain applied in the substrate at high temperature. The photoluminescence peak energy of GaAs on Si becomes almost the same as that of the stress‐free GaAs on GaAs grown by liquid phase epitaxy by applying this method.