Electrochemical reaction is one of the reactions which occur at solid/liquid interfaces. In the last three decades, relationships between reactivity and structure of solid/liquid interface, especially, electrode surface structure were uncovered using various techniques. Thus, nowadays it has been well recognized the importance of the study of electrode surface structures in in situ condition. However, dynamics of electrode surface structure has been well uncovered because the time resolution of scanning probe microscopes is not enough fast to monitor electrochemical processes. Surface X-ray scattering (SXS) is one of the in situ techniques which can be applied to the study of the solid/liquid interface structures. Especially, SXS is suitable for dynamics study. One of the advantages of SXS is that measurements can be carried out under ideal electrochemical conditions, i. e., low solution resistance and ideal diffusion condition. In this review, dynamics in underpotential deposition process of Bi on Au(111) electrode studied using surface X-ray scattering will be reported.