The stroboscopic phase shifting ESPI (SPS-ESPI), one of the optical vibration amplitude measurement techniques, is presented. Although the general PS-ESPI can be used for quantitative deformation measurement of the object, this technique cannot measure the vibration amplitude with itself only. The phase change due to the vibration of the object cannot be calculated with general PS-ESPI correctly. Therefore, in order to solve this problem, the stroboscopic illumination must be introduced to the general PS-ESPI. This can be done by using a device called as AOM (Acousto-Optic Modulator). In this paper, SPS-ESPI is applied to measure the vibration amplitude of the square plate whose all edges were fixed. The natural frequencies and mode shapes are analyzed by using ANSYS. And the results obtained by using SPS-ESPI technique are compared with that of the ANSYS analysis. The vibration amplitude is measured by using SPS-ESPI quantitatively.