We performed an ultrasonic measurement for the heavy-fermion compound CeRhIn_5 to investigate the origin of the field-induced anisotropic phase in high magnetic fields. The transverse elastic constant C_T=(C_{11}−C_{12})/2 and the ultrasonic attenuation coefficient αT show clear anomaly at B^★=28.5T, which was discussed as the electronic nematic transition point. In addition, C_T exhibits acoustic de Haas-van Alphen oscillation below 28.5 T. These elastic anomalies around B★ indicate an electric quadrupole ordering of O_{x^2−y^2} accompanied by B_{1g} crystal symmetry breaking and Fermi surface reconstruction due to the quadrupole-strain coupling, which results from itinerant 4f electrons and the p−f hybridized state.