We present an alternative method for determining the shear deformation potential b of the valence band in III-V semiconductors. Instead of bulk semiconductors we use quantum well structures and apply uniaxial stress perpendicular to the growth direction. Using analytical solutions wo show that the first confined hole state has a pronounced and characteristic nonlinear energy shift with respect to stress. This allows the hydrostatic and shear deformation potentials a and b to be determined independently from the stress dependence of the bandgap only, which can be measured by a wider range of experimental techniques than those necessary for obtaining deformation potentials from bulk material. Measurements on a (GaAs)10/(AlAs)10 superlattice yielded a value for b which is in good agreement with recent results from bulk measurements and hence support the validity of our proposed method.