A fuel cell includes a fuel electrode, an oxygen electrode, an electrolytic solution, a fuel flow passage, etc. The fuel electrode and the oxygen electrode are composed of a catalyst layer, a diffusion layer, and a collector, respectively. A methanol aqueous solution, etc. is continuously supplied to the fuel flow passage. Catalyst particulates consisting of platinum, ruthenium, palladium, etc. are in a dispersed state in the electrolytic solution. If a portion of fuel, such as methanol, passes through the fuel electrode as unreacted, and diffuses through the electrolytic solution to move to the oxygen electrode, oxidation reduction reactions between the methanol, and the oxygen which moves to the fuel electrode from the oxygen electrode are efficiently caused by the catalyst particulates so as to cancel each other. From the above are provided an electrolytic solution with high crossover blocking performance suitable for electrochemical devices, such as direct methanol fuel cells, and an electrochemical device using the electrolytic solution.