We report the first photoreflectance measurement of strain-induced piezoelectric field in a (111)B InGaAs/GaAs structure. The InGaAs quantum well was pseudomorphically grown in the undoped regions of a GaAs undoped-heavily doped structure. Four structures, two each with the same layer structures but different orientation, (111)B and (100), were used in this study. The electric fields in the undoped GaAs region were measured by Franz-Keldysh oscillations in photoreflectance. All the samples have a surface barrier height of about 0.7 eV. However, the measured electric field is 30% stronger in the (111)B sample compared to the (100) sample. We attribute this difference to the strain-induced electric field in the (111)B sample. The piezoelectric field in (111)B strained In0.15Ga0.85As obtained in this measurement is 2.2±0.5×105 V/cm, which agrees very well with theory.