A method for inspecting a process solution is provided. In this method, a process solution is disposed on a surface of a substrate. A liquid of the process solution is removed to form an inspection sample by a spinning method. The surface of the substrate of the inspection sample is inspected by the surface inspection device to identify whether a residue of the process solution is left on the surface of the substrate after removing the liquid of the process solution. Further, an apparatus for inspecting a process solution and a sample preparation apparatus in inspection are also provided herein.