Abstract: Provided is an open cell-type apparatus for producing sodium hypochlorite based on electrolysis using soft water and salt. The apparatus includes: a sodium hypochlorite generator including a plurality of electrode plates supported by a support, a flow channel for air flow provided above the support and the electrode plates, and an air intake hole and an air exhaust hole which communicate with the flow channel; a cooling unit for lowering a temperature of the flow channel; and a controller for controlling operation of the cooling unit by detecting a temperature of the sodium hypochlorite generator. The apparatus constantly maintains an optimum temperature of the sodium hypochlorite generator in order to produce sodium hypochlorite of a high concentration with high efficiency.