Worldwide consumption of vegetable soybean bas been increasing recently, hence it is necessary to produce good quality of soybean in our farms. In the process of vegetable soybean production threshing and seperation work accounts for about 80% of overall labor. Therefore, developing of the vegetable soybean thresher is necessary to reduce the cost of labor. The purpose of this study is to acquire the basic informations to design of the vegetable soybeans-thresher. We make the experimental system which measure the physical properties and investigate the detachment forces. Also, We calculated the minimum speed of threshing cylinder. The result are as follows; 1. The average length of soybean stem is 68.2cm. 2. The length of soybean pods are seen as 61.3mm for 3 grain, 52.6mm fer 2 grains and 41.0mm fer 1 grain 3. The widths of soybean pods are seen as 14.1mm fer 3 grain, 13.8mm fer 2 grains and 13.4mm fer 1 grain. 4. The weights of soybean pods are seen as 4.1grams for 3 grains, 2.7grams for 2 grains and 1.4grams for 1 grain. 5. The average detachment forces of pods are seen as 1.5kgf for 3 grains, 1.2kgf for 2 grains and 0.8kgf for 1 grain respectively For 1 grain, the detachment force of pods ranges from 0.2kgf to 1.4kgf. For 2 grains, the minimum detachment force of pods is seen as 0.6kgf and the maximum one is seen as 2.5kgf. For 3 grains, the minimum detachment force of pods is seen as 0.7kgf and the maximum one is seen as 2.7kgf. 6. The minimum speed of threshing cylinder is shown 6.83m/s.