Practical process of electrolytic manufacture of sugar was examined as to the electrolytic method and the effect of ξ potential of diaphragm in a two-chamber type. As a result, it was found that the three-chamber method in which acid saccharifying solution is placed in the middle chamber effected too large a ξ potential of the porcelain plate due to high voltage, and the movement of the acid saccharifying solution to the cathode chamber became greater before electrolytic neutralization could be expected. In a two-chamber process, using gelatine coated porcelain diaphragm, the passage of acid ions became slightly easier but on the other hand acid saccharifying solution (cathode solution) filtrated into the anode chamber resulting in too great a loss of sugar. This rules out the advisability of gelatine coating of the diaphragm. From the point of increasing monosaccharide by electrolysis it seemed most advantageous to employ a two-chamber process of electrolysis using a porcelain diaphragm.