In recent years, the Korean Army made use of fork-lifters or conveyors when loading and/or unloading military material in order to prevent accidents and to promote efficiency of military material handling activities. However, in troops smaller thin battalions, manual material handling activities are still committed for many reasons. In this thesis, a brand new loading/unloading device for efficient military material handling or manual workers was developed, and its validation study was conducted through objective assessment based on electromyography, subjective assessment based on Body-Map technique developed by Corlett and Bishop, and finally work performance comparison. The results of EMG analysis showed that muscular workload improved by 24% when using the device compared to manual work without the device, and complain of each body part was remarkably reduced. In addition, remarkable effectiveness enhancement was observed in the work performance. Consequently, it could be concluded that ergonomic devices like one developed in this research should be studied further in the ergonomic sense as well as in the economical sense.