We developed a new acoustic-resonance microscopy, electromagnetic-resonance- ultrasound microscopy (ERUM), to map a material?fs elastic constant in a local surface region. It is based on the resonance-frequency shift of a langasite (La3Ga5SiO14) crystal excited by an electric field from a surrounding solenoid coil: no electrodes were used. The acoustic coupling is made only at the tip of the crystal touching the specimen surface.?@Analysis on the dynamic contact stiffness with the Rayleigh-Ritz method deduced the local elastic constant from the resonance frequency. As an illustrating example, Young?fs modulus distribution of a duplex stainless steel is presented, which shows good agreement with the existing study.