We have found large effect of mechanical modifications on the magnetic anisotropy in thin films of (Ga,Mn)As on GaAs substrates and on (In,Ga)As buffer layers. Such modifications are simply brought about with etching two-dimensional films into thin-wires, which process partly releases compressive or tensile strains in the thin films. The effect of such mechanical processing depends on the etching depth, through which we can control the magnetic anisotropy. Uniaxial in-plane magnetic anisotropy has disappeared with releasing the strain, which result suggests that the uniaxial anisotropy is due to some extrinsic effect in one hand, that the dimer formation model is not the case on the other hand. (c) 2012 Elsevier B.V. All rights reserved.