Liquid atomization is the process of reducing the particle size and increasing the number of particles by reducing the liquid mass into a group of microparticles. The process of droplet collapse has been studied in detail by high-speed photography and simulations that take surface tension into account, including changes in shape. In this study, we attempted to clarify the unsteady pressure change in the interference between a droplet and a high-speed fluid by studying the pressure change downstream of the droplet and to construct quantitative data for comparison with calculation results. By using a straight small-volume shock tube, the pressure fluctuation was observed in synchronization with a high-speed camera image taken by an interfering droplet with a high-speed flow that occurs in a very short period of time. The results showed that the droplet was hardly affected by the shock wave but was affected by the high-speed jet following the shock wave. The larger the pressure ratio, the larger the difference in the pressure peak values with and without droplet, and the longer the time interval between the shock wave and the high-velocity jet. These quantitative results indicate that atomization of droplet in unsteady flow fields involves a drop in downstream pressure that cannot be obtained only by image processing of droplet shape change.