Distributions of transient and local lattice strains on resonating AT-cut quartz oscillators were measured in situ by scanning time-resolved X-ray diffraction under an alternating electric field to reveal the effects of the crystal shape and electrode thickness on their piezoelectric vibration. The concentration of the lattice vibration amplitude and energy at the electrode center in a plano-convex type oscillator and enhancement of the lattice strain in a plano–plano type oscillator within the electrode area with increasing electrode thickness have been unambiguously demonstrated by the method without any surface modifications.