In a sulfuric acid electrolytic cell to electrolyze sulfuric acid supplied to an anode compartment and a cathode compartment comprising a diaphragm, said anode compartment and said cathode compartment separated by said diaphragm, a cathode provided in said cathode compartment and a conductive diamond anode provided in said anode compartment, as said conductive diamond anode, a conductive diamond film is formed on the surface of said conductive substrate, the rear face of said conductive substrate is pasted, with conductive paste, on an current collector comprising a rigid body with size equal to, or larger than, said conductive substrate, an anode compartment frame constituting said anode compartment is contacted via gasket with the periphery on the side of the conductive diamond film of said diamond anode, said diaphragm is contacted with the front face of said anode compartment, further, with the front face of said diaphragm, the cathode compartment frame constituting said cathode compartment, a gasket, and said cathode are contacted in sequence, the rear face of said cathode is pasted with conductive paste to the current collector comprising a rigid body with size equal to, or larger than, said cathode and electric power is supplied from one current collector to the other current collector via said conductive paste.