The present invention provides a method of making an electrochemical capacitor electrode including a collector and an electronically conductive porous layer formed on the collector, the porous layer containing at least an electronically conductive porous particle and a binder adapted to bind the porous particle; the method including a mixing step of mixing the binder and a porous particle with a solvent including an organic solvent usable in a nonaqueous electrolytic solution, the organic solvent existing on a surface of the porous particle. The present invention also provides a porous particle with a solvent, wherein an organic solvent usable in a nonaqueous electrolytic solution exists on the surface of a porous body having an electronic conductivity.