A refrigeration unit using ammonia aimed to reduce the amount of charged ammonia, and to establish a measure to render leaked ammonia gas harmless, is provided. The ammonia chiller unit comprises a compressor, a compressor driving motor, an evaporation type condenser, an expansion valve, an evaporator to perform refrigerating cycle using ammonia as a refrigerant. The unit is composed of a lower construction body comprising a compressor, a motor for driving the compressor, a control board, a brine cooler to function as an evaporator, a brine pump, a water tank, a sprinkler pump, etc., and an upper construction body comprising a drain pan and an evaporation type condenser located above the drain pan. The evaporation type condenser is composed of a multitubular heat exchanger having at both end sides an inlet and outlet headers, ammonia refrigerant flowing in one direction, and the multitubular heat exchanger is incline downward from the inlet side toward the evaporator.