This study has described as a way of establishing an automated system that allows sorting of living fish caught at sea by weight, and producing and testing as prototypes. The live fish that applied for this research is named as a croaker. 30(thirty) times of measurements with the fishes were applied for screening initially. As a results, it was the highest deviation rate of 19.7% within 2g of their initial weight. In addition, it showed the lowest deviation rate of 8.2% below 10g of them. Throughout the measuring experiments, it was found that the error that occurred during weighting was friction with the upper surface of the load cell on the circular sorting plate. Once the friction was removed, it was figured out that the average deviation in weight per each fish was measured as 0.76g. This error should be able to be eliminated by improving the material of machine elements, the surface material of the load cell. Under this circumstance, this pilot test in sorting living fishes by weight was brought adequate results. The existing sorting device was performed at 4,500 fishes per hour as a sorting speed. The sorting device developed in this research improved productivity by over 33% by setting the sorting speed in 6,000 fishes per hour.