An electrochemical reactor includes a positive electrode with a first major surface and a second major surface on an opposite side to the first major surface, and a negative electrode with a first major surface and a second major surface on an opposite side to the first major surface. The positive electrode and the negative electrode oppose each other by the first major surfaces thereof and are arranged to be apart from each other while defining a space therebetween. The space is filled with an electrically conductive liquid and/or a dielectric liquid. A first isolation member is provided on the first surface of the positive electrode to isolate the positive electrode from the liquid, and a second isolation member is provided on the first surface of the negative electrode to isolate the negative electrode from the liquid. The first isolation member includes a first liquid-repellent porous membrane including a plurality of pores, and the second isolation member includes a second liquid-repellent porous membrane including a plurality of pores. The reactor further includes a pressure-applying member which pressurizes the liquid to fill the pores of the first and second liquid-repellent porous membranes with the liquid, thereby causing an electrochemical reaction involving the positive electrode and the negative electrode.
