An anode (3) and a cathode (5), interposing a solid polymer film (7), are disposed. While supplying purified water from a supply port (13a) of an anode chamber (13), wherein the anode (3) is disposed, and a supply port (15a) of a cathode chamber (15), wherein the cathode (5) is disposed, direct electric current is applied between the anode (3) and the cathode (5). As a result, ozone-water is discharged from an outlet port (13b) of the anode chamber (13). In such an electrolysis cell (1), a free-standing conductive diamond plate, formed by microwave plasma assisted CVD so as to have a thickness of 0.8 mm, is used as the anode (3). The diamond plate is provided with holes, having a diameter of 1 mm and disposed such that a center distance therebetween becomes 2 mm. Therefore, the electrolysis cell (1) can stably produce ozone without causing exfoliation of the anode (3), even when high voltage and large current are applied between the anode (3) and the cathode (5).