Abstract: An electric quantity titrating device is disclosed of the type comprising electrolytic electrodes immersed in a solution to be analyzed for passing electrolytic current, detecting electrodes immersed in the solution, detecting apparatus connected across the detecting electrodes for producing a voltage signal which is used to continuously supply the electrolytic current to the electrolytic electrodes and integrating apparatus for integrating the electrolytic current for measuring the electric quantity required for the analysis until an end point is reached. A current controlling apparatus is provided in this system which includes a device for detecting the deviation of the voltage signal from a preset value at the end point, an amplifier for amplifying the deviation signal, and a current converter for converting the amplifed current into output current which is applied to the electrolytic electrodes.