Eu doped SrAl_2 O_4 and BaAl_2 O_4 were prepared by solid state reaction method added with H_3 BO_3 as a flux. We developed a new measuring equipment for Mechano-luminescence (ML) which was emitted by application of vibration stress generated by a piezo actuator.SrAl_2 O_4 emitted broad green light identified from Eu^<2+> in Photoluminescence (PL) and ML. The both intensities of luminescence from BaAl_2 O_4 showed weaker than that from SrAl_2 O_4 caused by the difference in the symmetry of each crystalline structure.