The present invention provides a chlorine dioxide manufacturing device that can accurately control the amount of chlorine dioxide produced. The present invention provides a chlorine dioxide gas manufacturing device comprising an electrolysis chamber, a liquid surface level measuring chamber, and a bubbling gas feeding device. The electrolysis chamber and the liquid surface level measuring chamber each comprises an electrolytic solution and a gas, wherein the electrolytic solution comprises an aqueous chlorite solution, and the electrolysis chamber and the liquid surface level measuring chamber are joined to each other above each liquid surface via a gas piping and joined to each other below each liquid surface via an electrolytic solution piping so that the height of the electrolytic solutions contained in each chamber are substantially equal.