NOVELTY - An electrolyte solution (30) contains catalyst microparticles in dispersed state. An electrochemical device comprises an electrode (A), an electrode (B) arranged opposite to the electrode (A), and the electrolyte solution between the electrodes (A,B). A reacting material (a) is supplied in the side of electrode (A). A reacting material (b) is supplied in the side of electrode (B). An oxidation reduction reaction is carried out through the electrodes (A,B).    USE - Electrolyte solution is used for electrochemical device used as fuel cell (both claimed) such as alkali electrolyte-type fuel cell, phosphoric acid fuel cell, molten carbonate type fuel cell, solid oxide fuel cell, polymer electrolyte fuel cell and direct methanol fuel cell used as energy source of mobile device and electric vehicle. Can also be used for capacitor, flammable material sensor and display.    ADVANTAGE - The electrolyte solution has high crossover inhibiting properties.    DETAILED DESCRIPTION - An electrolyte solution contains catalyst microparticles in dispersed state. An electrochemical device comprises an electrode (A), an electrode (B) arranged opposite to the electrode (A), and the electrolyte solution between the electrodes (A,B). A reacting material (a) is supplied in the side of electrode (A). A reacting material (b) is supplied in the side of electrode (B). An oxidation reduction reaction is carried out through the electrodes (A,B). The reacting material (a) does not react on the electrode (A), diffuses inside of the electrolyte solution, and moves to the electrode (B). The reacting material (b) does not react on the electrode (B), diffuses inside of the electrolyte solution, and moves to the electrode (A). Reaction cancelled mutually by oxidation reduction reaction is accelerated by catalyst microparticles. The catalyst microparticles contain platinum, ruthenium, palladium, and/or gold. The reacting material (a) is alcohol or hydrogen. The reacting material (b) is oxygen. The electrolyte solution is acidic electrolyte solution containing inorganic acid, organic acid and/or hydrogen-ion dissociative solid microparticles, preferably sulfuric acid, sulfonic-acid type organic compound and/or sulfonic-acid type cation-exchange-resin microparticles as electrolyte. Alternately, the electrolyte solution is basic electrolyte solution containing inorganic base, organic base and/or hydroxide ion dissociative solid microparticles, preferably hydroxide of alkali metal, quaternary ammonium compound and/or quaternary-ammonium-compound type anion exchange resin microparticles as electrolyte.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the fuel cell. (Drawing includes non-English language text)    Fuel electrode (10)    Catalyst layer (11)    Diffused layer (12)    Oxygen electrode (20)    Electrolyte solution (30)