A cell dedicated to the characterization of the electrolyte side of the Li/electrolyte interface is developed. The reflected X‐rays from the electrolyte side of the Li/electrolyte interface are measured using the developed cell. The total reflection X‐ray of the Li/electrolyte interface is successfully detected, and the critical angle is near the calculated value. In addition, the critical angle after the application of current is also in good agreement with the calculated value. Furthermore, grazing‐incidence X‐ray scattering measurements show characteristic signals that may reflect the structural change of the electrolyte, resulting from the redox reaction at the interface region. Small changes are captured in the scattering pattern of the electrolyte in the interfacial region caused by oxidation and reduction.