the present invention relates to an electrolyzer for producing sodium hypochlorite by electrolyzing brine such as salt water or seawater and the like , and more specifically to a horizontal non - membrane type electrolyzer of a new structure which can maintain a constant interval among electrode plates without using a welding means or an adhering means on the inside of a housing by including a separator for dividing an inner space of a hollow type housing into a plurality of electrode chambers ; the electrode plates which are arranged in parallel to each other in the constant interval within a rectangular space part of the separator ; and a fixing bar for fixing the separator to an inner wall of the housing .