Surface X-ray scattering (SXS) technique is ideal to determine the three-dimensional structure at the solid/liquid interfaces with a high spatial resolution. When elements with an atomic number next to each other exist at the interface, however, the interfacial structure cannot be precisely determined from the normal SXS meausrements, because the values of the atomic scattering parameters of each element are too near. Using the anomalous scattering effect, the resonance SXS (RSXS) method was proposed and carried out under ultra high vacuum (UHV). We applied this RSXS method to the solid/liquid interface, i. e., electrochemically deposited Pt layer on Au(111) surface in the electrolyte solution, and demonstrated that the anomalous scattering parameter effect is utilized at the solid/liquid interfaces.